diff --git a/cfg.go b/cfg.go
index c368667..c97201a 100644
--- a/cfg.go
+++ b/cfg.go
@@ -48,6 +48,7 @@ type cfg struct {
 	ServersString  []string `json:"default_servers"`
 	servers        []addr
 	Timeout        int      `json:"timeout"`
+	TTL            int      `json:"ttl"`
 	BlacklistFiles []string `json:"blacklist_ips"`
 	blacklistIps   item
 	Rules          []Rule `json:"rules"`
diff --git a/example_config/config.json b/example_config/config.json
index 0c43fc5..e4bc881 100644
--- a/example_config/config.json
+++ b/example_config/config.json
@@ -1,6 +1,7 @@
 {
     "listen":["tcp:0.0.0.0:8053","udp::8053"],
     "default_servers":["tcp:208.67.222.222:53","tcp:8.8.8.8:53"],
+    "ttl":3600,
     "timeout":1,
     "blacklist_ips":["ip.txt"],
     "rules":[
diff --git a/routers.go b/routers.go
index 8f0a5ed..896ca7c 100644
--- a/routers.go
+++ b/routers.go
@@ -116,7 +116,7 @@ func initRouters(c *cfg) {
 		c,
 		&dns.Client{Net: "tcp", Timeout: time.Duration(c.Timeout) * time.Second},
 		&dns.Client{Net: "udp", Timeout: time.Duration(c.Timeout) * time.Second},
-		newCache(1000, 5*60*60), // cache 5 hours
+		newCache(1000, int64(c.TTL)), // cache 5 hours
 	}
 	dns.Handle(".", router)
 }