diff --git a/packet/conn.go b/packet/conn.go
index c60f68e66..60de437c4 100644
--- a/packet/conn.go
+++ b/packet/conn.go
@@ -3,15 +3,14 @@ package packet
 import (
 	"bufio"
 	"bytes"
-	"io"
-	"net"
-	"sync"
-
 	"crypto/rand"
 	"crypto/rsa"
 	"crypto/sha1"
 	"crypto/x509"
 	"encoding/pem"
+	"io"
+	"net"
+	"sync"
 
 	. "github.com/go-mysql-org/go-mysql/mysql"
 	"github.com/go-mysql-org/go-mysql/utils"
@@ -97,10 +96,28 @@ func (c *Conn) ReadPacketReuseMem(dst []byte) ([]byte, error) {
 
 	if err := c.ReadPacketTo(buf); err != nil {
 		return nil, errors.Trace(err)
+	}
+
+	readBytes := buf.Bytes()
+	readSize := len(readBytes)
+	var result []byte
+	if len(dst) > 0 {
+		result = append(dst, readBytes...)
+		// if read block is big, do not cache buf any more
+		if readSize > utils.TooBigBlockSize {
+			buf = nil
+		}
 	} else {
-		result := append(dst, buf.Bytes()...)
-		return result, nil
+		if readSize > utils.TooBigBlockSize {
+			// if read block is big, use read block as result and do not cache buf any more
+			result = readBytes
+			buf = nil
+		} else {
+			result = append(dst, readBytes...)
+		}
 	}
+
+	return result, nil
 }
 
 func (c *Conn) copyN(dst io.Writer, src io.Reader, n int64) (written int64, err error) {
diff --git a/utils/bytes_buffer_pool.go b/utils/bytes_buffer_pool.go
index a1ca8707d..fe0066ed2 100644
--- a/utils/bytes_buffer_pool.go
+++ b/utils/bytes_buffer_pool.go
@@ -5,6 +5,10 @@ import (
 	"sync"
 )
 
+const (
+	TooBigBlockSize = 1024 * 1024 * 4
+)
+
 var (
 	bytesBufferPool = sync.Pool{
 		New: func() interface{} {
@@ -27,6 +31,10 @@ func BytesBufferGet() (data *bytes.Buffer) {
 }
 
 func BytesBufferPut(data *bytes.Buffer) {
+	if data == nil || len(data.Bytes()) > TooBigBlockSize {
+		return
+	}
+
 	select {
 	case bytesBufferChan <- data:
 	default: