diff --git a/lower/nic.go b/lower/nic.go
index 676f970..c688bf2 100644
--- a/lower/nic.go
+++ b/lower/nic.go
@@ -20,6 +20,7 @@ type NIC struct {
 	ifce   *water.Interface
 	ip     string
 	subnet string
+	mtu    string
 	cidrs  []string
 }
 
@@ -27,7 +28,7 @@ type NIC struct {
 // 网卡地址为 ip, 所属子网为 subnet
 // 以本网卡为下一跳的所有子网为 cidrs
 // cidrs 不包括本网卡 subnet
-func NewNIC(ip, subnet string, cidrs ...string) NICIO {
+func NewNIC(ip, subnet, mtu string, cidrs ...string) NICIO {
 	ifce, err := water.New(water.Config{DeviceType: water.TUN})
 	if err != nil {
 		panic(err)
@@ -35,8 +36,9 @@ func NewNIC(ip, subnet string, cidrs ...string) NICIO {
 	n := &NIC{
 		ifce:   ifce,
 		ip:     ip,
-		cidrs:  cidrs,
 		subnet: subnet,
+		mtu:    mtu,
+		cidrs:  cidrs,
 	}
 	return n
 }
diff --git a/lower/tun_darwin.go b/lower/tun_darwin.go
index b1f4649..745d551 100644
--- a/lower/tun_darwin.go
+++ b/lower/tun_darwin.go
@@ -4,6 +4,7 @@
 package lower
 
 func (n *NIC) Up() {
+	execute("ifconfig", n.ifce.Name(), "mtu", n.mtu)
 	execute("ifconfig", n.ifce.Name(), "inet", n.ip, n.ip, "up")
 	execute("route", "add", n.subnet, "-interface", n.ifce.Name())
 	for _, c := range n.cidrs {
diff --git a/lower/tun_linux.go b/lower/tun_linux.go
index f77e7ce..6b991ef 100644
--- a/lower/tun_linux.go
+++ b/lower/tun_linux.go
@@ -4,7 +4,7 @@
 package lower
 
 func (n *NIC) Up() {
-	execute("/sbin/ip", "link", "set", "dev", n.ifce.Name(), "mtu", "1500")
+	execute("/sbin/ip", "link", "set", "dev", n.ifce.Name(), "mtu", n.mtu)
 	execute("/sbin/ip", "addr", "add", n.ip, "dev", n.ifce.Name())
 	execute("/sbin/ip", "link", "set", "dev", n.ifce.Name(), "up")
 	execute("/sbin/ip", "route", "add", n.subnet, "dev", n.ifce.Name())
diff --git a/lower/tun_windows.go b/lower/tun_windows.go
index 514c56f..e676195 100644
--- a/lower/tun_windows.go
+++ b/lower/tun_windows.go
@@ -11,7 +11,7 @@ func (n *NIC) Up() {
 	if err != nil {
 		panic(err)
 	}
-	execute("cmd", "/c", "netsh interface ip set address name=\""+n.ifce.Name()+"\" source=static addr=\""+n.ip+"\" mask=\""+(net.IP)(ipn.Mask).String()+"\" gateway=none")
+	execute("cmd", "/c", "netsh interface ip set address name=\""+n.ifce.Name()+"\" source=static addr=\""+n.ip+"\" mask=\""+(net.IP)(ipn.Mask).String()+"\" gateway=none mtu="+n.mtu)
 	for _, c := range n.cidrs {
 		ip, cidr, err := net.ParseCIDR(c)
 		if err != nil {
diff --git a/upper/services/wg/wg.go b/upper/services/wg/wg.go
index 28561c1..47625ad 100644
--- a/upper/services/wg/wg.go
+++ b/upper/services/wg/wg.go
@@ -2,6 +2,7 @@ package wg
 
 import (
 	"errors"
+	"fmt"
 	"net"
 
 	base14 "github.com/fumiama/go-base16384"
@@ -92,7 +93,7 @@ func (wg *WG) init(srcport, destport, mtu uint16) {
 		&wg.key,
 		wg.c.IP+"/32",
 		wg.c.EndPoint,
-		lower.NewNIC(wg.c.IP, wg.c.SubNet, cidrs...),
+		lower.NewNIC(wg.c.IP, wg.c.SubNet, fmt.Sprintf("%d", mtu), cidrs...),
 		srcport, destport, mtu,
 	)