diff --git a/cmd/utils/cmd.go b/cmd/utils/cmd.go
index f8f7f6376e..983762db8f 100644
--- a/cmd/utils/cmd.go
+++ b/cmd/utils/cmd.go
@@ -21,6 +21,7 @@ import (
 	"bufio"
 	"fmt"
 	"io"
+	"math"
 	"math/big"
 	"os"
 	"os/signal"
@@ -152,6 +153,7 @@ func InitOlympic() {
 	params.MaximumExtraDataSize = big.NewInt(1024)
 	NetworkIdFlag.Value = 0
 	core.BlockReward = big.NewInt(1.5e+18)
+	core.ExpDiffPeriod = big.NewInt(math.MaxInt64)
 }
 
 func FormatTransactionData(data string) []byte {
diff --git a/core/chain_util.go b/core/chain_util.go
index 34f6c8d0aa..84b462ce3d 100644
--- a/core/chain_util.go
+++ b/core/chain_util.go
@@ -32,7 +32,7 @@ import (
 var (
 	blockHashPre  = []byte("block-hash-")
 	blockNumPre   = []byte("block-num-")
-	expDiffPeriod = big.NewInt(100000)
+	ExpDiffPeriod = big.NewInt(100000)
 )
 
 // CalcDifficulty is the difficulty adjustment algorithm. It returns
@@ -57,7 +57,7 @@ func CalcDifficulty(time, parentTime uint64, parentNumber, parentDiff *big.Int)
 	}
 
 	periodCount := new(big.Int).Add(parentNumber, common.Big1)
-	periodCount.Div(periodCount, expDiffPeriod)
+	periodCount.Div(periodCount, ExpDiffPeriod)
 	if periodCount.Cmp(common.Big1) > 0 {
 		// diff = diff + 2^(periodCount - 2)
 		expDiff := periodCount.Sub(periodCount, common.Big2)