diff --git a/consensus/istanbul/backend/snapshot.go b/consensus/istanbul/backend/snapshot.go
index 08be3a25149e..4ab8d94256a4 100644
--- a/consensus/istanbul/backend/snapshot.go
+++ b/consensus/istanbul/backend/snapshot.go
@@ -22,6 +22,7 @@ import (
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/consensus/istanbul"
+	"github.com/ethereum/go-ethereum/consensus/istanbul/validator"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
 )
@@ -50,11 +51,11 @@ type Tally struct {
 type Snapshot struct {
 	Epoch uint64 // The number of blocks after which to checkpoint and reset the pending votes
 
-	Number uint64                   `json:"number"`     // Block number where the snapshot was created
-	Hash   common.Hash              `json:"hash"`       // Block hash where the snapshot was created
-	Votes  []*Vote                  `json:"votes"`      // List of votes cast in chronological order
-	Tally  map[common.Address]Tally `json:"tally"`      // Current vote tally to avoid recalculating
-	ValSet istanbul.ValidatorSet    `json:"validators"` // Set of authorized validators at this moment
+	Number uint64                   // Block number where the snapshot was created
+	Hash   common.Hash              // Block hash where the snapshot was created
+	Votes  []*Vote                  // List of votes cast in chronological order
+	Tally  map[common.Address]Tally // Current vote tally to avoid recalculating
+	ValSet istanbul.ValidatorSet    // Set of authorized validators at this moment
 }
 
 // newSnapshot create a new snapshot with the specified startup parameters. This
@@ -272,3 +273,49 @@ func (s *Snapshot) validators() []common.Address {
 	}
 	return validators
 }
+
+type snapshotJSON struct {
+	Epoch  uint64                   `json:"epoch"`
+	Number uint64                   `json:"number"`
+	Hash   common.Hash              `json:"hash"`
+	Votes  []*Vote                  `json:"votes"`
+	Tally  map[common.Address]Tally `json:"tally"`
+
+	// for validator set
+	Validators []common.Address        `json:"validators"`
+	Policy     istanbul.ProposerPolicy `json:"policy"`
+}
+
+func (s *Snapshot) toJSONStruct() *snapshotJSON {
+	return &snapshotJSON{
+		Epoch:      s.Epoch,
+		Number:     s.Number,
+		Hash:       s.Hash,
+		Votes:      s.Votes,
+		Tally:      s.Tally,
+		Validators: s.validators(),
+		Policy:     s.ValSet.Policy(),
+	}
+}
+
+// Unmarshal from a json byte array
+func (s *Snapshot) UnmarshalJSON(b []byte) error {
+	var j snapshotJSON
+	if err := json.Unmarshal(b, &j); err != nil {
+		return err
+	}
+
+	s.Epoch = j.Epoch
+	s.Number = j.Number
+	s.Hash = j.Hash
+	s.Votes = j.Votes
+	s.Tally = j.Tally
+	s.ValSet = validator.NewSet(j.Validators, j.Policy)
+	return nil
+}
+
+// Marshal to a json byte array
+func (s *Snapshot) MarshalJSON() ([]byte, error) {
+	j := s.toJSONStruct()
+	return json.Marshal(j)
+}
diff --git a/consensus/istanbul/backend/snapshot_test.go b/consensus/istanbul/backend/snapshot_test.go
index e00a05c97780..829f333b23e5 100644
--- a/consensus/istanbul/backend/snapshot_test.go
+++ b/consensus/istanbul/backend/snapshot_test.go
@@ -20,10 +20,12 @@ import (
 	"bytes"
 	"crypto/ecdsa"
 	"math/big"
+	"reflect"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/consensus/istanbul"
+	"github.com/ethereum/go-ethereum/consensus/istanbul/validator"
 	"github.com/ethereum/go-ethereum/core"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/core/vm"
@@ -400,3 +402,54 @@ func TestVoting(t *testing.T) {
 		}
 	}
 }
+
+func TestSaveAndLoad(t *testing.T) {
+	snap := &Snapshot{
+		Epoch:  5,
+		Number: 10,
+		Hash:   common.HexToHash("1234567890"),
+		Votes: []*Vote{
+			{
+				Validator: common.StringToAddress("1234567891"),
+				Block:     15,
+				Address:   common.StringToAddress("1234567892"),
+				Authorize: false,
+			},
+		},
+		Tally: map[common.Address]Tally{
+			common.StringToAddress("1234567893"): Tally{
+				Authorize: false,
+				Votes:     20,
+			},
+		},
+		ValSet: validator.NewSet([]common.Address{
+			common.StringToAddress("1234567894"),
+			common.StringToAddress("1234567895"),
+		}, istanbul.RoundRobin),
+	}
+	db, _ := ethdb.NewMemDatabase()
+	err := snap.store(db)
+	if err != nil {
+		t.Errorf("store snapshot failed: %v", err)
+	}
+
+	snap1, err := loadSnapshot(snap.Epoch, db, snap.Hash)
+	if err != nil {
+		t.Errorf("load snapshot failed: %v", err)
+	}
+	if snap.Epoch != snap1.Epoch {
+		t.Errorf("epoch mismatch: have %v, want %v", snap1.Epoch, snap.Epoch)
+	}
+	if snap.Hash != snap1.Hash {
+		t.Errorf("hash mismatch: have %v, want %v", snap1.Number, snap.Number)
+	}
+	if !reflect.DeepEqual(snap.Votes, snap.Votes) {
+		t.Errorf("votes mismatch: have %v, want %v", snap1.Votes, snap.Votes)
+	}
+	if !reflect.DeepEqual(snap.Tally, snap.Tally) {
+		t.Errorf("tally mismatch: have %v, want %v", snap1.Tally, snap.Tally)
+	}
+	if !reflect.DeepEqual(snap.ValSet, snap.ValSet) {
+		t.Errorf("validator set mismatch: have %v, want %v", snap1.ValSet, snap.ValSet)
+	}
+}
diff --git a/consensus/istanbul/validator.go b/consensus/istanbul/validator.go
index a96487cf9fbb..e0d142866e10 100644
--- a/consensus/istanbul/validator.go
+++ b/consensus/istanbul/validator.go
@@ -71,6 +71,8 @@ type ValidatorSet interface {
 	Copy() ValidatorSet
 	// Get the maximum number of faulty nodes
 	F() int
+	// Get proposer policy
+	Policy() ProposerPolicy
 }
 
 // ----------------------------------------------------------------------------
diff --git a/consensus/istanbul/validator/default.go b/consensus/istanbul/validator/default.go
index f10c2beedb3c..17edda55216b 100644
--- a/consensus/istanbul/validator/default.go
+++ b/consensus/istanbul/validator/default.go
@@ -41,16 +41,18 @@ func (val *defaultValidator) String() string {
 // ----------------------------------------------------------------------------
 
 type defaultSet struct {
-	validators  istanbul.Validators
+	validators istanbul.Validators
+	policy     istanbul.ProposerPolicy
+
 	proposer    istanbul.Validator
 	validatorMu sync.RWMutex
-
-	selector istanbul.ProposalSelector
+	selector    istanbul.ProposalSelector
 }
 
-func newDefaultSet(addrs []common.Address, selector istanbul.ProposalSelector) *defaultSet {
+func newDefaultSet(addrs []common.Address, policy istanbul.ProposerPolicy) *defaultSet {
 	valSet := &defaultSet{}
 
+	valSet.policy = policy
 	// init validators
 	valSet.validators = make([]istanbul.Validator, len(addrs))
 	for i, addr := range addrs {
@@ -62,8 +64,10 @@ func newDefaultSet(addrs []common.Address, selector istanbul.ProposalSelector) *
 	if valSet.Size() > 0 {
 		valSet.proposer = valSet.GetByIndex(0)
 	}
-	//set proposal selector
-	valSet.selector = selector
+	valSet.selector = roundRobinProposer
+	if policy == istanbul.Sticky {
+		valSet.selector = stickyProposer
+	}
 
 	return valSet
 }
@@ -189,7 +193,9 @@ func (valSet *defaultSet) Copy() istanbul.ValidatorSet {
 	for _, v := range valSet.validators {
 		addresses = append(addresses, v.Address())
 	}
-	return newDefaultSet(addresses, valSet.selector)
+	return NewSet(addresses, valSet.policy)
 }
 
 func (valSet *defaultSet) F() int { return int(math.Ceil(float64(valSet.Size())/3)) - 1 }
+
+func (valSet *defaultSet) Policy() istanbul.ProposerPolicy { return valSet.policy }
diff --git a/consensus/istanbul/validator/default_test.go b/consensus/istanbul/validator/default_test.go
index dd8d63820228..987ed12c84f1 100644
--- a/consensus/istanbul/validator/default_test.go
+++ b/consensus/istanbul/validator/default_test.go
@@ -78,7 +78,7 @@ func testNormalValSet(t *testing.T) {
 	val1 := New(addr1)
 	val2 := New(addr2)
 
-	valSet := newDefaultSet([]common.Address{addr1, addr2}, roundRobinProposer)
+	valSet := newDefaultSet([]common.Address{addr1, addr2}, istanbul.RoundRobin)
 	if valSet == nil {
 		t.Errorf("the format of validator set is invalid")
 		t.FailNow()
@@ -182,7 +182,7 @@ func testStickyProposer(t *testing.T) {
 	val1 := New(addr1)
 	val2 := New(addr2)
 
-	valSet := newDefaultSet([]common.Address{addr1, addr2}, stickyProposer)
+	valSet := newDefaultSet([]common.Address{addr1, addr2}, istanbul.Sticky)
 
 	// test get proposer
 	if val := valSet.GetProposer(); !reflect.DeepEqual(val, val1) {
diff --git a/consensus/istanbul/validator/validator.go b/consensus/istanbul/validator/validator.go
index c4bdad61cbcf..9a1e15c2d8fc 100644
--- a/consensus/istanbul/validator/validator.go
+++ b/consensus/istanbul/validator/validator.go
@@ -28,15 +28,7 @@ func New(addr common.Address) istanbul.Validator {
 }
 
 func NewSet(addrs []common.Address, policy istanbul.ProposerPolicy) istanbul.ValidatorSet {
-	switch policy {
-	case istanbul.RoundRobin:
-		return newDefaultSet(addrs, roundRobinProposer)
-	case istanbul.Sticky:
-		return newDefaultSet(addrs, stickyProposer)
-	}
-
-	// use round-robin policy as default proposal policy
-	return newDefaultSet(addrs, roundRobinProposer)
+	return newDefaultSet(addrs, policy)
 }
 
 func ExtractValidators(extraData []byte) []common.Address {