diff --git a/.gitignore b/.gitignore
index b339b06..8b5b812 100644
--- a/.gitignore
+++ b/.gitignore
@@ -22,6 +22,7 @@ _testmain.go
 *.exe
 *.test
 config.json
+*.log
 *.swp
 godns
 
@@ -29,4 +30,4 @@ vendor/*
 /.idea
 /godns.iml
 /godns.ipr
-/godns.iws
\ No newline at end of file
+/godns.iws
diff --git a/dns_handler.go b/dns_handler.go
index 10509ed..a8e6cd1 100644
--- a/dns_handler.go
+++ b/dns_handler.go
@@ -13,7 +13,7 @@ import (
 	"github.com/bitly/go-simplejson"
 )
 
-func get_currentIP(url string) (string, error) {
+func getCurrentIP(url string) (string, error) {
 	response, err := http.Get(url)
 
 	if err != nil {
@@ -27,13 +27,13 @@ func get_currentIP(url string) (string, error) {
 	return string(body), nil
 }
 
-func generate_header(content url.Values) url.Values {
+func generateHeader(content url.Values) url.Values {
 	header := url.Values{}
-	if(Configuration.LoginToken!=""){
-		header.Add("login_token", Configuration.LoginToken)
-	}else{
-		header.Add("login_email", Configuration.Email)
-		header.Add("login_password", Configuration.Password)
+	if configuration.LoginToken != "" {
+		header.Add("login_token", configuration.LoginToken)
+	} else {
+		header.Add("login_email", configuration.Email)
+		header.Add("login_password", configuration.Password)
 	}
 	header.Add("format", "json")
 	header.Add("lang", "en")
@@ -48,11 +48,11 @@ func generate_header(content url.Values) url.Values {
 	return header
 }
 
-func api_version() {
-	post_data("/Info.Version", nil)
+func apiVersion() {
+	postData("/Info.Version", nil)
 }
 
-func get_domain(name string) int64 {
+func getDomain(name string) int64 {
 
 	var ret int64
 	values := url.Values{}
@@ -60,17 +60,17 @@ func get_domain(name string) int64 {
 	values.Add("offset", "0")
 	values.Add("length", "20")
 
-	response, err := post_data("/Domain.List", values)
+	response, err := postData("/Domain.List", values)
 
 	if err != nil {
 		log.Println("Failed to get domain list...")
 		return -1
 	}
 
-	sjson, parse_err := simplejson.NewJson([]byte(response))
+	sjson, parseErr := simplejson.NewJson([]byte(response))
 
-	if parse_err != nil {
-		log.Println(parse_err)
+	if parseErr != nil {
+		log.Println(parseErr)
 		return -1
 	}
 
@@ -100,16 +100,16 @@ func get_domain(name string) int64 {
 	return ret
 }
 
-func get_subdomain(domain_id int64, name string) (string, string) {
-	log.Println("debug:", domain_id, name)
+func getSubDomain(domainID int64, name string) (string, string) {
+	log.Println("debug:", domainID, name)
 	var ret, ip string
 	value := url.Values{}
-	value.Add("domain_id", strconv.FormatInt(domain_id, 10))
+	value.Add("domain_id", strconv.FormatInt(domainID, 10))
 	value.Add("offset", "0")
 	value.Add("length", "1")
 	value.Add("sub_domain", name)
 
-	response, err := post_data("/Record.List", value)
+	response, err := postData("/Record.List", value)
 
 	if err != nil {
 		log.Println("Failed to get domain list")
@@ -144,7 +144,7 @@ func get_subdomain(domain_id int64, name string) (string, string) {
 	return ret, ip
 }
 
-func update_ip(domain_id int64, sub_domain_id string, sub_domain_name string, ip string) {
+func updateIP(domain_id int64, sub_domain_id string, sub_domain_name string, ip string) {
 	value := url.Values{}
 	value.Add("domain_id", strconv.FormatInt(domain_id, 10))
 	value.Add("record_id", sub_domain_id)
@@ -153,7 +153,7 @@ func update_ip(domain_id int64, sub_domain_id string, sub_domain_name string, ip
 	value.Add("record_line", "默认")
 	value.Add("value", ip)
 
-	response, err := post_data("/Record.Modify", value)
+	response, err := postData("/Record.Modify", value)
 
 	if err != nil {
 		log.Println("Failed to update record to new IP!")
@@ -174,13 +174,13 @@ func update_ip(domain_id int64, sub_domain_id string, sub_domain_name string, ip
 
 }
 
-func post_data(url string, content url.Values) (string, error) {
+func postData(url string, content url.Values) (string, error) {
 	client := &http.Client{}
-	values := generate_header(content)
+	values := generateHeader(content)
 	req, _ := http.NewRequest("POST", "https://dnsapi.cn"+url, strings.NewReader(values.Encode()))
 
 	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
-	req.Header.Set("User-Agent", fmt.Sprintf("GoDNS/0.1 (%s)", Configuration.Email))
+	req.Header.Set("User-Agent", fmt.Sprintf("GoDNS/0.1 (%s)", configuration.Email))
 
 	response, err := client.Do(req)
 	defer response.Body.Close()
diff --git a/dns_handler_test.go b/dns_handler_test.go
index d428a54..21f3ee1 100644
--- a/dns_handler_test.go
+++ b/dns_handler_test.go
@@ -4,8 +4,8 @@ import (
 	"testing"
 )
 
-func Test_get_current_IP(t *testing.T) {
-	ip, _ := get_currentIP("http://members.3322.org/dyndns/getip")
+func testGetCurrentIP(t *testing.T) {
+	ip, _ := getCurrentIP("http://members.3322.org/dyndns/getip")
 
 	if ip == "" {
 		t.Log("IP is empty...")
diff --git a/godns.go b/godns.go
index a719004..2905432 100644
--- a/godns.go
+++ b/godns.go
@@ -16,7 +16,7 @@ const (
 )
 
 var (
-	Configuration Settings
+	configuration Settings
 	optConf       = flag.String("c", "./config.json", "config file")
 	optCommand    = flag.String("s", "", "send signal to a master process: stop, quit, reopen, reload")
 	optHelp       = flag.Bool("h", false, "this help")
@@ -35,7 +35,13 @@ func main() {
 	}
 
 	var err error
-	Configuration, err = LoadSettings(*optConf)
+	configuration, err = LoadSettings(*optConf)
+
+	err = InitLogger(configuration.Log_Path, configuration.Log_Size, configuration.Log_Num)
+	if err != nil {
+		log.Println("InitLogger error:", err)
+		return
+	}
 
 	if err != nil {
 		fmt.Println(err.Error())
@@ -60,20 +66,20 @@ func dns_loop() {
 
 	for {
 
-		domain_id := get_domain(Configuration.Domain)
+		domain_id := getDomain(configuration.Domain)
 
 		if domain_id == -1 {
 			continue
 		}
 
-		currentIP, err := get_currentIP(Configuration.IP_Url)
+		currentIP, err := getCurrentIP(configuration.IP_Url)
 
 		if err != nil {
 			log.Println("get_currentIP:", err)
 			continue
 		}
 
-		sub_domain_id, ip := get_subdomain(domain_id, Configuration.Sub_domain)
+		sub_domain_id, ip := getSubDomain(domain_id, configuration.Sub_domain)
 
 		if sub_domain_id == "" || ip == "" {
 			log.Println("sub_domain:", sub_domain_id, ip)
@@ -85,7 +91,7 @@ func dns_loop() {
 		//Continue to check the IP of sub-domain
 		if len(ip) > 0 && !strings.Contains(currentIP, ip) {
 			log.Println("Start to update record IP...")
-			update_ip(domain_id, sub_domain_id, Configuration.Sub_domain, currentIP)
+			updateIP(domain_id, sub_domain_id, configuration.Sub_domain, currentIP)
 		} else {
 			log.Println("Current IP is same as domain IP, no need to update...")
 		}
diff --git a/logger.go b/logger.go
new file mode 100644
index 0000000..a6474c1
--- /dev/null
+++ b/logger.go
@@ -0,0 +1,292 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"runtime/debug"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+const (
+	L_INFO int = iota
+	L_WARNING
+	L_DEBUG
+	PRE_INFO    = "[   INFO]"
+	PRE_WARNING = "[WARNING]"
+	PRE_DEBUG   = "[  DEBUG]"
+)
+
+type Logger struct {
+	DEV_MODE      bool
+	fd            *os.File
+	size          int
+	num           int
+	level         int
+	mu            sync.Mutex
+	muSplit       sync.Mutex
+	flushInterval int64 //Second
+	flushSize     int
+	buf           *bytes.Buffer
+	log           *log.Logger
+}
+
+func NewLogger(logfile string, size, num int, level int, flushInterval int64, flushSize int) (logger *Logger, err error) {
+	if size < 1 || num < 1 || level < L_INFO || len(logfile) < 1 {
+		err = errors.New("NewLogWriter:param error.")
+		return
+	}
+	logger = &Logger{size: size * 1024, num: num, level: level, DEV_MODE: false}
+	logger.fd, err = os.OpenFile(logfile, os.O_WRONLY|os.O_APPEND|os.O_CREATE, os.ModeAppend|0666)
+	if err != nil {
+		logger = nil
+		return
+	}
+	log.SetOutput(logger)
+	if flushInterval > 0 && flushSize > 0 {
+		logger.buf = new(bytes.Buffer)
+		logger.log = log.New(logger.buf, "", log.LstdFlags)
+
+		go func(interval int64, logger *Logger) {
+			defer func() {
+				if r := recover(); r != nil {
+					log.Printf("logger Tick, Recovered in %v:\n %s", r, debug.Stack())
+				}
+			}()
+			c := time.Tick(time.Duration(interval) * time.Second)
+			for _ = range c {
+				logger.Flush()
+			}
+		}(flushInterval, logger)
+	}
+	return
+}
+
+func InitLogger(logfile string, size, num int) (err error) {
+	logger, err := NewLogger(logfile, size, num, L_INFO, -1, -1)
+	if logger != nil {
+		logger.level = L_INFO - 1
+	}
+	return
+}
+
+//immplement write
+func (this *Logger) Write(p []byte) (n int, err error) {
+	if this.DEV_MODE {
+		n, err = os.Stdout.Write(p)
+		return
+	}
+	n, err = this.fd.Write(p)
+	if err == nil {
+		fi, e := this.fd.Stat()
+		if e != nil {
+			err = e
+			return
+		}
+		if fi.Size() > int64(this.size) {
+			this.muSplit.Lock()
+			defer this.muSplit.Unlock()
+
+			fname := fi.Name()
+			strings.HasSuffix(fname, ".log")
+			fbase := fname[:len(fname)-3]
+
+			oldBs := make([]byte, 0, this.size)
+			newBs := []byte{}
+			fd, e := os.Open(fname)
+			if e != nil {
+				err = e
+				return
+			}
+			rd := bufio.NewReader(fd)
+			for {
+				line, e := rd.ReadBytes('\n')
+				if e == io.EOF {
+					break
+				}
+				if e != nil {
+					err = e
+					return
+				}
+				if len(oldBs)+len(line) > this.size {
+					newBs = append(newBs, line...)
+				} else {
+					oldBs = append(oldBs, line...)
+				}
+			}
+			fd.Close()
+
+			_, err = this.saveLog(1, fbase, oldBs)
+			if err != nil {
+				return
+			}
+			err = this.fd.Close()
+			if err != nil {
+				return
+			}
+			err = os.Remove(fname)
+			if err != nil {
+				return
+			}
+			this.fd, err = os.OpenFile(fname, os.O_WRONLY|os.O_APPEND|os.O_CREATE, os.ModeAppend|0666)
+			if err != nil {
+				return
+			}
+			_, err = this.fd.Write(newBs)
+			if err != nil {
+				return
+			}
+		}
+	}
+	return
+}
+
+func (this *Logger) saveLog(index int, fbase string, data []byte) (n int, err error) {
+	fn := fbase + strconv.Itoa(index) + ".log"
+	_, err = os.Stat(fn)
+	if index < this.num && err == nil {
+		var b []byte
+		b, err = ioutil.ReadFile(fn)
+		if err != nil {
+			return
+		}
+		n, err = this.saveLog(index+1, fbase, b)
+		if err != nil {
+			return
+		}
+	}
+
+	fd, err := os.OpenFile(fn, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, os.ModePerm|0666)
+	if err != nil {
+		return
+	}
+	defer fd.Close()
+	n, err = fd.Write(data)
+	return
+}
+
+//flush buf data to std log
+func (this *Logger) Flush() {
+	if this.buf.Len() > 0 {
+		this.mu.Lock()
+		defer this.mu.Unlock()
+
+		log.SetFlags(0)
+		log.Print(this.buf)
+		log.SetFlags(log.LstdFlags)
+		this.buf.Reset()
+	}
+}
+
+//clean prefix and check buf size
+func (this *Logger) clean() {
+	this.log.SetPrefix("")
+	if this.buf.Len()/1024 > this.flushSize {
+		go this.Flush()
+	}
+}
+
+func (this *Logger) setPrefix(lv int) bool {
+	if lv > this.level {
+		return false
+	}
+
+	switch lv {
+	case L_INFO:
+		this.log.SetPrefix(PRE_INFO)
+	case L_WARNING:
+		this.log.SetPrefix(PRE_WARNING)
+	case L_DEBUG:
+		this.log.SetPrefix(PRE_DEBUG)
+	default:
+		return false
+	}
+	return true
+}
+
+func (this *Logger) logPrint(lv int, args ...interface{}) {
+	this.mu.Lock()
+	defer this.mu.Unlock()
+
+	if !this.setPrefix(lv) {
+		return
+	}
+	this.log.Print(args...)
+	this.clean()
+}
+
+func (this *Logger) logPrintln(lv int, args ...interface{}) {
+	this.mu.Lock()
+	defer this.mu.Unlock()
+
+	if !this.setPrefix(lv) {
+		return
+	}
+	this.log.Println(args...)
+	this.clean()
+}
+
+func (this *Logger) logPrintf(lv int, format string, args ...interface{}) {
+	this.mu.Lock()
+	defer this.mu.Unlock()
+
+	if !this.setPrefix(lv) {
+		return
+	}
+	this.log.Printf(format, args...)
+	this.clean()
+}
+
+//close fd
+func (this *Logger) Close() {
+	if this.fd != nil {
+		this.Flush()
+		this.fd.Close()
+	}
+}
+
+func (this *Logger) Info(args ...interface{}) {
+	this.logPrint(L_INFO, args...)
+}
+
+func (this *Logger) Infoln(args ...interface{}) {
+	this.logPrintln(L_INFO, args...)
+}
+
+func (this *Logger) Infof(format string, args ...interface{}) {
+	this.logPrintf(L_INFO, format, args...)
+}
+
+func (this *Logger) Warning(args ...interface{}) {
+	this.logPrint(L_WARNING, args...)
+}
+
+func (this *Logger) Warningln(args ...interface{}) {
+	this.logPrintln(L_WARNING, args...)
+}
+
+func (this *Logger) Warningf(format string, args ...interface{}) {
+	this.logPrintf(L_WARNING, format, args...)
+}
+
+func (this *Logger) Debug(args ...interface{}) {
+	this.logPrint(L_DEBUG, args...)
+	this.Flush()
+}
+
+func (this *Logger) Debugln(args ...interface{}) {
+	this.logPrintln(L_DEBUG, args...)
+	this.Flush()
+}
+
+func (this *Logger) Debugf(format string, args ...interface{}) {
+	this.logPrintf(L_DEBUG, format, args...)
+	this.Flush()
+}