diff --git a/util/expensivequery/expensivequerey_test.go b/util/expensivequery/expensivequerey_test.go
new file mode 100644
index 0000000000000..066db5873ab1a
--- /dev/null
+++ b/util/expensivequery/expensivequerey_test.go
@@ -0,0 +1,74 @@
+// Copyright 2019 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package expensivequery
+
+import (
+	"testing"
+	"time"
+
+	. "github.com/pingcap/check"
+	"github.com/pingcap/tidb/sessionctx/stmtctx"
+	"github.com/pingcap/tidb/util"
+	"github.com/pingcap/tidb/util/memory"
+	"github.com/pingcap/tidb/util/testleak"
+)
+
+func TestT(t *testing.T) {
+	TestingT(t)
+}
+
+type testSuite struct{}
+
+func (s *testSuite) SetUpSuite(c *C)    {}
+func (s *testSuite) TearDownSuite(c *C) {}
+func (s *testSuite) SetUpTest(c *C)     { testleak.BeforeTest() }
+func (s *testSuite) TearDownTest(c *C)  { testleak.AfterTest(c)() }
+
+var _ = Suite(&testSuite{})
+
+func (s *testSuite) TestLogFormat(c *C) {
+	mem := new(memory.Tracker)
+	mem.Consume(1<<30 + 1<<29 + 1<<28 + 1<<27)
+	info := &util.ProcessInfo{
+		ID:            233,
+		User:          "PingCAP",
+		Host:          "127.0.0.1",
+		DB:            "Database",
+		Info:          "select * from table where a > 1",
+		CurTxnStartTS: 23333,
+		StatsInfo: func(interface{}) map[string]uint64 {
+			return nil
+		},
+		StmtCtx: &stmtctx.StatementContext{
+			MemTracker: mem,
+		},
+	}
+	costTime := time.Second * 233
+	logFields := genLogFields(costTime, info)
+	c.Assert(len(logFields), Equals, 7)
+	c.Assert(logFields[0].Key, Equals, "cost_time")
+	c.Assert(logFields[0].String, Equals, "233s")
+	c.Assert(logFields[1].Key, Equals, "conn_id")
+	c.Assert(logFields[1].Integer, Equals, int64(233))
+	c.Assert(logFields[2].Key, Equals, "user")
+	c.Assert(logFields[2].String, Equals, "PingCAP")
+	c.Assert(logFields[3].Key, Equals, "database")
+	c.Assert(logFields[3].String, Equals, "Database")
+	c.Assert(logFields[4].Key, Equals, "txn_start_ts")
+	c.Assert(logFields[4].Integer, Equals, int64(23333))
+	c.Assert(logFields[5].Key, Equals, "mem_max")
+	c.Assert(logFields[5].String, Equals, "2013265920 Bytes (1.875 GB)")
+	c.Assert(logFields[6].Key, Equals, "sql")
+	c.Assert(logFields[6].String, Equals, "select * from table where a > 1")
+}
diff --git a/util/expensivequery/expensivequery.go b/util/expensivequery/expensivequery.go
index 996a53dcdf7be..2143754c182e7 100644
--- a/util/expensivequery/expensivequery.go
+++ b/util/expensivequery/expensivequery.go
@@ -90,8 +90,7 @@ func (eqh *Handle) LogOnQueryExceedMemQuota(connID uint64) {
 	logExpensiveQuery(time.Since(info.Time), info)
 }
 
-// logExpensiveQuery logs the queries which exceed the time threshold or memory threshold.
-func logExpensiveQuery(costTime time.Duration, info *util.ProcessInfo) {
+func genLogFields(costTime time.Duration, info *util.ProcessInfo) []zap.Field {
 	logFields := make([]zap.Field, 0, 20)
 	logFields = append(logFields, zap.String("cost_time", strconv.FormatFloat(costTime.Seconds(), 'f', -1, 64)+"s"))
 	execDetail := info.StmtCtx.GetExecDetails()
@@ -138,7 +137,7 @@ func logExpensiveQuery(costTime time.Duration, info *util.ProcessInfo) {
 	}
 	logFields = append(logFields, zap.Uint64("txn_start_ts", info.CurTxnStartTS))
 	if memTracker := info.StmtCtx.MemTracker; memTracker != nil {
-		logFields = append(logFields, zap.String("mem_max", memTracker.BytesToString(memTracker.MaxConsumed())))
+		logFields = append(logFields, zap.String("mem_max", fmt.Sprintf("%d Bytes (%v)", memTracker.MaxConsumed(), memTracker.BytesToString(memTracker.MaxConsumed()))))
 	}
 
 	const logSQLLen = 1024 * 8
@@ -150,6 +149,10 @@ func logExpensiveQuery(costTime time.Duration, info *util.ProcessInfo) {
 		sql = fmt.Sprintf("%s len(%d)", sql[:logSQLLen], len(sql))
 	}
 	logFields = append(logFields, zap.String("sql", sql))
+	return logFields
+}
 
-	logutil.BgLogger().Warn("expensive_query", logFields...)
+// logExpensiveQuery logs the queries which exceed the time threshold or memory threshold.
+func logExpensiveQuery(costTime time.Duration, info *util.ProcessInfo) {
+	logutil.BgLogger().Warn("expensive_query", genLogFields(costTime, info)...)
 }