diff --git a/mysql/const.go b/mysql/const.go
index 3bc12e84..735d3ce4 100644
--- a/mysql/const.go
+++ b/mysql/const.go
@@ -173,6 +173,7 @@ var (
 	TK_ID_SELECT      = 11
 	TK_ID_START       = 12
 	TK_ID_TRANSACTION = 13
+	TK_ID_SHOW        = 14
 
 	PARSE_TOKEN_MAP = map[string]int{
 		"insert":      TK_ID_INSERT,
@@ -188,6 +189,7 @@ var (
 		"use":         TK_ID_USE,
 		"start":       TK_ID_START,
 		"transaction": TK_ID_TRANSACTION,
+		"show":        TK_ID_SHOW,
 	}
 	// '/'
 	COMMENT_PREFIX uint8 = 47
diff --git a/proxy/server/conn.go b/proxy/server/conn.go
index 0f9cc6e9..ebea15a8 100644
--- a/proxy/server/conn.go
+++ b/proxy/server/conn.go
@@ -252,10 +252,7 @@ func (c *ClientConn) readHandshakeResponse() error {
 		//if connect without database, use default db
 		db = c.proxy.schema.db
 	}
-
-	if err := c.useDB(db); err != nil {
-		return err
-	}
+	c.db = db
 
 	return nil
 }
@@ -317,11 +314,7 @@ func (c *ClientConn) dispatch(data []byte) error {
 	case mysql.COM_PING:
 		return c.writeOK(nil)
 	case mysql.COM_INIT_DB:
-		if err := c.useDB(hack.String(data)); err != nil {
-			return err
-		} else {
-			return c.writeOK(nil)
-		}
+		return c.handleUseDB(hack.String(data))
 	case mysql.COM_FIELD_LIST:
 		return c.handleFieldList(data)
 	case mysql.COM_STMT_PREPARE:
@@ -345,27 +338,6 @@ func (c *ClientConn) dispatch(data []byte) error {
 	return nil
 }
 
-func (c *ClientConn) useDB(db string) error {
-	if c.schema == nil {
-		return mysql.NewDefaultError(mysql.ER_NO_DB_ERROR)
-	}
-
-	nodeName := c.schema.rule.DefaultRule.Nodes[0]
-
-	n := c.proxy.GetNode(nodeName)
-	co, err := n.GetMasterConn()
-	defer c.closeConn(co, false)
-	if err != nil {
-		return err
-	}
-
-	if err = co.UseDB(db); err != nil {
-		return err
-	}
-	c.db = db
-	return nil
-}
-
 func (c *ClientConn) writeOK(r *mysql.Result) error {
 	if r == nil {
 		r = &mysql.Result{Status: c.status}
diff --git a/proxy/server/conn_preshard.go b/proxy/server/conn_preshard.go
index 1289422a..776a68ff 100644
--- a/proxy/server/conn_preshard.go
+++ b/proxy/server/conn_preshard.go
@@ -127,6 +127,9 @@ func (c *ClientConn) GetTransExecDB(tokens []string, sql string) (*ExecuteDB, er
 	tokensLen := len(tokens)
 	executeDB := new(ExecuteDB)
 
+	//transaction execute in master db
+	executeDB.IsSlave = false
+
 	if 2 <= tokensLen {
 		if tokens[0][0] == mysql.COMMENT_PREFIX {
 			nodeName := strings.Trim(tokens[0], mysql.COMMENT_STRING)
@@ -144,8 +147,6 @@ func (c *ClientConn) GetTransExecDB(tokens []string, sql string) (*ExecuteDB, er
 		if executeDB == nil {
 			return nil, nil
 		}
-		//transaction execute in master db
-		executeDB.IsSlave = false
 		return executeDB, nil
 	}
 	if len(c.txConns) == 1 && c.txConns[executeDB.ExecNode] == nil {
@@ -171,6 +172,8 @@ func (c *ClientConn) GetExecDB(tokens []string, sql string) (*ExecuteDB, error)
 				return c.getUpdateExecDB(tokens, tokensLen)
 			case mysql.TK_ID_SET:
 				return c.getSetExecDB(tokens, tokensLen, sql)
+			case mysql.TK_ID_SHOW:
+				return c.getShowExecDB(tokens, tokensLen)
 			default:
 				return nil, nil
 			}
@@ -359,3 +362,17 @@ func (c *ClientConn) getSetExecDB(tokens []string, tokensLen int, sql string) (*
 
 	return executeDB, nil
 }
+
+//get the execute database for show sql
+//choose slave preferentially
+func (c *ClientConn) getShowExecDB(tokens []string, tokensLen int) (*ExecuteDB, error) {
+	executeDB := new(ExecuteDB)
+	executeDB.IsSlave = true
+
+	err := c.setExecuteNode(tokens, tokensLen, executeDB)
+	if err != nil {
+		return nil, err
+	}
+
+	return executeDB, nil
+}
diff --git a/proxy/server/conn_query.go b/proxy/server/conn_query.go
index 7000de23..cf00d56f 100644
--- a/proxy/server/conn_query.go
+++ b/proxy/server/conn_query.go
@@ -93,7 +93,7 @@ func (c *ClientConn) handleQuery(sql string) (err error) {
 	case *sqlparser.AdminHelp:
 		return c.handleAdminHelp(v)
 	case *sqlparser.UseDB:
-		return c.handleUseDB(v)
+		return c.handleUseDB(v.DB)
 	case *sqlparser.SimpleSelect:
 		return c.handleSimpleSelect(v)
 	default:
diff --git a/proxy/server/conn_use.go b/proxy/server/conn_use.go
index 14885720..5b709f29 100644
--- a/proxy/server/conn_use.go
+++ b/proxy/server/conn_use.go
@@ -17,13 +17,16 @@ package server
 import (
 	"fmt"
 
+	"github.com/flike/kingshard/backend"
 	"github.com/flike/kingshard/mysql"
-	"github.com/flike/kingshard/sqlparser"
 )
 
-func (c *ClientConn) handleUseDB(stmt *sqlparser.UseDB) error {
-	if len(stmt.DB) == 0 {
-		return fmt.Errorf("must have database, not %s", sqlparser.String(stmt))
+func (c *ClientConn) handleUseDB(dbName string) error {
+	var co *backend.BackendConn
+	var err error
+
+	if len(dbName) == 0 {
+		return fmt.Errorf("must have database, the length of dbName is zero")
 	}
 	if c.schema == nil {
 		return mysql.NewDefaultError(mysql.ER_NO_DB_ERROR)
@@ -32,15 +35,19 @@ func (c *ClientConn) handleUseDB(stmt *sqlparser.UseDB) error {
 	nodeName := c.schema.rule.DefaultRule.Nodes[0]
 
 	n := c.proxy.GetNode(nodeName)
-	co, err := n.GetMasterConn()
+	//get the connection from slave preferentially
+	co, err = n.GetSlaveConn()
+	if err != nil {
+		co, err = n.GetMasterConn()
+	}
 	defer c.closeConn(co, false)
 	if err != nil {
 		return err
 	}
 
-	if err = co.UseDB(string(stmt.DB)); err != nil {
+	if err = co.UseDB(dbName); err != nil {
 		return err
 	}
-	c.db = string(stmt.DB)
+	c.db = dbName
 	return c.writeOK(nil)
 }