diff --git a/.gitignore b/.gitignore
index cb756e9ec..f7bba6a08 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 vendor
-.idea
\ No newline at end of file
+.idea
+build
\ No newline at end of file
diff --git a/docs/modules/README.md b/docs/modules/README.md
new file mode 100644
index 000000000..742280230
--- /dev/null
+++ b/docs/modules/README.md
@@ -0,0 +1,53 @@
+# Upgrade Module
+
+本module作为支持区块链软件平滑升级的基础设施，通过upgradeProposal和switch两阶段的投票来在约定高度切换到新版的代码，并对历史版本的链上数据完全兼容。
+
+key point：
+
+* upgradeProposal投票通过后各个节点下载安装新版本软件，并启动软件发送switch投票，表明已经可以切换到新版本
+* switch的投票将在约定高度进行检查，需要95%的Voting Power才视为投票通过
+* switch通过后开启切换流程：
+   1. check_tx全部返回fail，以拒绝新tx的处理
+   2. 处理mempool中留存的tx，直到生成一个empty block
+   3. 配置新版本的路由开关，并打开check_tx接受新tx
+* 发生老版本AppHash冲突，检查自己是否在switch voter list中，否则reset rootMultiStore到上一个commit，并下载新版本开始同步block
+* 新增Module的升级方式（现有Module逻辑修改也通过新Module完成），新老版本的Module共享同一个store，对于查询需要路由到相应版本的Module
+* Hardcord的升级方式（bug fix），Upgrade Module提供便利函数来决定指定的代码段在当前区块高度是否执行
+
+## Data Struct
+
+```
+type ModuleLifeTime struct {
+	Start	int64
+	End	int64
+        Handler sdk.Handler
+	store	sdk.KVStoreKey
+}
+
+type Version struct {
+	Id		int	 // should be equal with corresponding upgradeProposalID
+	Start		int64
+	ModuleList	[]ModuleLifeTime
+}
+
+```
+
+## TxMsg
+
+```
+type MsgSwitch struct {
+	Title          string
+	ProposalId     int
+	Voter          sdk.AccAddress
+}
+
+```
+
+## Storage
+
+| Key | Type   | Value | Description | Note|
+| --------- | ------ | ------- | -------- | -----------|
+| CurrentVersionIDKey | int | CurrentVersionID    | c/     |    |
+| VersionKey | Version | Version    | v/%010d/     |  v/proposalId  |
+| VersionListKey | ListOfVersionKey | [][]byte{}    | l/     |  list of the version_key ordered by proposalId  |
+| SwitchKey | MsgSwitch | MsgSwitch    | s/%010d/%d/     | s/proposalId/switchVoterAddress | 
diff --git a/modules/upgrade/error.go b/modules/upgrade/error.go
new file mode 100644
index 000000000..f08addf7f
--- /dev/null
+++ b/modules/upgrade/error.go
@@ -0,0 +1,33 @@
+package upgrade
+
+import (
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+const (
+	DefaultCodespace sdk.CodespaceType = 1
+
+	CodeInvalidMsgType			sdk.CodeType = 200
+	CodeUnknownRequest  		sdk.CodeType = sdk.CodeUnknownRequest
+)
+
+func codeToDefaultMsg(code sdk.CodeType) string {
+	switch code {
+	case CodeInvalidMsgType:
+		return "Invalid msg type"
+	default:
+		return sdk.CodeToDefaultMsg(code)
+	}
+}
+
+func NewError(codespace sdk.CodespaceType, code sdk.CodeType, msg string) sdk.Error {
+	msg = msgOrDefaultMsg(msg, code)
+	return sdk.NewError(codespace, code, msg)
+}
+
+func msgOrDefaultMsg(msg string, code sdk.CodeType) string {
+	if msg != "" {
+		return msg
+	}
+	return codeToDefaultMsg(code)
+}
\ No newline at end of file
diff --git a/modules/upgrade/handler.go b/modules/upgrade/handler.go
new file mode 100644
index 000000000..81ed44773
--- /dev/null
+++ b/modules/upgrade/handler.go
@@ -0,0 +1,31 @@
+package upgrade
+
+import (
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"reflect"
+	"fmt"
+)
+
+func NewHandler(k Keeper) sdk.Handler {
+	return func(ctx sdk.Context, msg sdk.Msg) sdk.Result {
+		switch msg := msg.(type) {
+		case MsgSwitch:
+			return handlerSwitch(ctx, msg, k)
+		default:
+			errMsg := "Unrecognized Upgrade Msg type: " + reflect.TypeOf(msg).Name()
+			return sdk.ErrUnknownRequest(errMsg).Result()
+		}
+	}
+}
+
+func handlerSwitch(ctx sdk.Context, msg sdk.Msg, k Keeper) sdk.Result {
+	msgSwitch, ok := msg.(MsgSwitch)
+	if !ok {
+		return NewError(DefaultCodespace, CodeInvalidMsgType, "Handler should only receive MsgSwitch").Result()
+	}
+
+	return sdk.Result{
+		Code: 0,
+		Log:  fmt.Sprintf("Switch %s by %s", msgSwitch.Title, msgSwitch.Voter.String()),
+	}
+}
diff --git a/modules/upgrade/keeper.go b/modules/upgrade/keeper.go
new file mode 100644
index 000000000..63c68a992
--- /dev/null
+++ b/modules/upgrade/keeper.go
@@ -0,0 +1,36 @@
+package upgrade
+
+import (
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	"github.com/cosmos/cosmos-sdk/wire"
+	"github.com/cosmos/cosmos-sdk/x/bank"
+)
+
+type ModuleLifeTime struct {
+	Start		int64
+	End			int64
+	Handler 	sdk.Handler
+	store		sdk.KVStoreKey
+}
+
+type Version struct {
+	Id			int		// should be equal with corresponding upgradeProposalID
+	Start		int64
+	ModuleList	[]ModuleLifeTime
+}
+
+type Keeper struct {
+	storeKey   		sdk.StoreKey
+	cdc        		*wire.Codec
+	coinKeeper 		bank.Keeper
+}
+
+func NewKeeper(cdc *wire.Codec, key sdk.StoreKey, ck bank.Keeper) Keeper {
+	keeper := Keeper {
+		storeKey:   key,
+		cdc:        cdc,
+		coinKeeper: ck,
+	}
+	return keeper
+}
+
diff --git a/modules/upgrade/keeper_keys.go b/modules/upgrade/keeper_keys.go
new file mode 100644
index 000000000..739431810
--- /dev/null
+++ b/modules/upgrade/keeper_keys.go
@@ -0,0 +1,24 @@
+package upgrade
+
+import (
+	"fmt"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+var (
+	CurrentVersionIDKey	= []byte("c/")
+	VersionKey 			= "v/%010d/"		// v/<proposalId>
+	SwitchKey			= "s/%010d/%d/"		// s/<proposalId>/<switchVoterAddress>
+)
+
+func GetCurrentVersionIDKey() []byte {
+	return CurrentVersionIDKey
+}
+
+func GetVersionKey(proposalID int64) []byte {
+	return []byte(fmt.Sprintf(VersionKey, proposalID))
+}
+
+func GetSwitchKey(proposalID int64, switchVoterAddr sdk.AccAddress) []byte {
+	return []byte(fmt.Sprintf(SwitchKey, proposalID, switchVoterAddr))
+}
diff --git a/modules/upgrade/msgs.go b/modules/upgrade/msgs.go
new file mode 100644
index 000000000..b03e799f4
--- /dev/null
+++ b/modules/upgrade/msgs.go
@@ -0,0 +1,32 @@
+package upgrade
+
+import (
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+type MsgSwitch struct {
+	Title		string
+	ProposalID	int
+	Voter		sdk.AccAddress
+}
+
+
+func (msg MsgSwitch) Type() string {
+	return "record"
+}
+
+func (msg MsgSwitch) GetSignBytes() []byte {
+	b, err := msgCdc.MarshalJSON(msg)
+	if err != nil {
+		panic(err)
+	}
+	return b
+}
+
+func (msg MsgSwitch) ValidateBasic() sdk.Error {
+	return nil
+}
+
+func (msg MsgSwitch) GetSigners() []sdk.AccAddress {
+	return []sdk.AccAddress{msg.Voter}
+}
diff --git a/modules/upgrade/wire.go b/modules/upgrade/wire.go
new file mode 100644
index 000000000..f66ff68c1
--- /dev/null
+++ b/modules/upgrade/wire.go
@@ -0,0 +1,16 @@
+package upgrade
+
+import (
+	"github.com/cosmos/cosmos-sdk/wire"
+)
+
+// Register concrete types on wire codec
+func RegisterWire(cdc *wire.Codec) {
+	cdc.RegisterConcrete(MsgSwitch{}, "iris-hub/MsgSwitch", nil)
+}
+
+var msgCdc = wire.NewCodec()
+
+func init() {
+	RegisterWire(msgCdc)
+}