diff --git a/Dockerfile b/Dockerfile
index 3dda97b..596b75c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -22,6 +22,7 @@ ENV PROXY=direct://
 ENV MTU=9000
 ENV RESTAPI=
 ENV UDP_TIMEOUT=
+ENV UDP_RLYBUF=
 ENV TCP_SNDBUF=
 ENV TCP_RCVBUF=
 ENV TCP_AUTO_TUNING=
diff --git a/common/pool/pool.go b/common/pool/pool.go
index 8bea3cb..fa87e14 100644
--- a/common/pool/pool.go
+++ b/common/pool/pool.go
@@ -7,9 +7,10 @@ const (
 	// MaxSegmentSize is the largest possible UDP datagram size.
 	MaxSegmentSize = (1 << 16) - 1
 
-	// io.Copy default buffer size is 32 KiB, but the maximum packet
-	// size of vmess/shadowsocks is about 16 KiB, so define a buffer
-	// of 20 KiB to reduce the memory of each TCP relay.
+	// RelayBufferSize is a buffer of 20 KiB to reduce the memory
+	// of each TCP relay as io.Copy default buffer size is 32 KiB,
+	// but the maximum packet size of vmess/shadowsocks is about
+	// 16 KiB, so define .
 	RelayBufferSize = 20 << 10
 )
 
diff --git a/engine/engine.go b/engine/engine.go
index e7cb863..2284d67 100644
--- a/engine/engine.go
+++ b/engine/engine.go
@@ -129,6 +129,14 @@ func general(k *Key) error {
 		}
 		tunnel.SetUDPTimeout(k.UDPTimeout)
 	}
+
+	if k.UDPRelayBufferSize != "" {
+		size, err := units.RAMInBytes(k.UDPRelayBufferSize)
+		if err != nil {
+			return err
+		}
+		tunnel.SetUDPRelayBufferSize(int(size))
+	}
 	return nil
 }
 
diff --git a/engine/key.go b/engine/key.go
index 32e39dc..fcbfcd7 100644
--- a/engine/key.go
+++ b/engine/key.go
@@ -13,7 +13,8 @@ type Key struct {
 	TCPModerateReceiveBuffer bool          `yaml:"tcp-moderate-receive-buffer"`
 	TCPSendBufferSize        string        `yaml:"tcp-send-buffer-size"`
 	TCPReceiveBufferSize     string        `yaml:"tcp-receive-buffer-size"`
+	UDPRelayBufferSize       string        `yaml:"udp-relay-buffer-size"`
+	UDPTimeout               time.Duration `yaml:"udp-timeout"`
 	TUNPreUp                 string        `yaml:"tun-pre-up"`
 	TUNPostUp                string        `yaml:"tun-post-up"`
-	UDPTimeout               time.Duration `yaml:"udp-timeout"`
 }
diff --git a/main.go b/main.go
index 7cc4b1f..e7aa992 100644
--- a/main.go
+++ b/main.go
@@ -35,6 +35,7 @@ func init() {
 	flag.StringVar(&key.RestAPI, "restapi", "", "HTTP statistic server listen address")
 	flag.StringVar(&key.TCPSendBufferSize, "tcp-sndbuf", "", "Set TCP send buffer size for netstack")
 	flag.StringVar(&key.TCPReceiveBufferSize, "tcp-rcvbuf", "", "Set TCP receive buffer size for netstack")
+	flag.StringVar(&key.UDPRelayBufferSize, "udp-rlybuf", "", "Set UDP relay buffer size for tunnel")
 	flag.BoolVar(&key.TCPModerateReceiveBuffer, "tcp-auto-tuning", false, "Enable TCP receive buffer auto-tuning")
 	flag.StringVar(&key.TUNPreUp, "tun-pre-up", "", "Execute a command before TUN device setup")
 	flag.StringVar(&key.TUNPostUp, "tun-post-up", "", "Execute a command after TUN device setup")
diff --git a/tunnel/udp.go b/tunnel/udp.go
index 1672de8..758aa77 100644
--- a/tunnel/udp.go
+++ b/tunnel/udp.go
@@ -15,13 +15,22 @@ import (
 	"github.com/xjasonlyu/tun2socks/v2/tunnel/statistic"
 )
 
-// _udpSessionTimeout is the default timeout for each UDP session.
-var _udpSessionTimeout = 60 * time.Second
+var (
+	// _udpSessionTimeout is the default timeout for each UDP session.
+	_udpSessionTimeout = 60 * time.Second
+
+	// _udpRelayBufferSize is the default size for UDP packets relay.
+	_udpRelayBufferSize = 16 << 10
+)
 
 func SetUDPTimeout(t time.Duration) {
 	_udpSessionTimeout = t
 }
 
+func SetUDPRelayBufferSize(size int) {
+	_udpRelayBufferSize = size
+}
+
 // TODO: Port Restricted NAT support.
 func handleUDPConn(uc adapter.UDPConn) {
 	defer uc.Close()
@@ -84,7 +93,7 @@ func relayPacket(left net.PacketConn, right net.PacketConn, to net.Addr) error {
 }
 
 func copyPacketBuffer(dst net.PacketConn, src net.PacketConn, to net.Addr, timeout time.Duration) error {
-	buf := pool.Get(pool.MaxSegmentSize)
+	buf := pool.Get(_udpRelayBufferSize)
 	defer pool.Put(buf)
 
 	for {