diff --git a/example/example.html b/example/example.html
index c4ea80b..6a76fbc 100644
--- a/example/example.html
+++ b/example/example.html
@@ -26,7 +26,7 @@
         function claimToken() {
             var email = Math.random() + "test@demo.io";
             var url = "https://testnet.nebulas.io/claim/api/claim/"+ email+ "/"+ account.getAddressString() +"/";
-            var request = new Neb.HttpRequest(url);
+            var request = new HttpRequest(url);
             request.request("GET", "", "").then(function (resp) {
                 console.log(resp);
             }).catch(function (err) {
diff --git a/lib/admin.js b/lib/admin.js
index 89b97d1..9a4b722 100644
--- a/lib/admin.js
+++ b/lib/admin.js
@@ -2,6 +2,7 @@
 "use strict";
 
 var utils = require('./utils/utils.js');
+var Transaction = require("./transaction.js");
 
 /**
  * Admin API constructor.
@@ -158,16 +159,7 @@ Admin.prototype.lockAccount = function (options) {
  */
 Admin.prototype.sendTransaction = function (options) {
     options = utils.argumentsToObject(['from', 'to', 'value', 'nonce', 'gasPrice', 'gasLimit', 'contract', 'binary'], arguments);
-    var params = {
-        "from": options.from,
-        "to": options.to,
-        "value": utils.toString(options.value),
-        "nonce": options.nonce,
-        "gasPrice": utils.toString(options.gasPrice),
-        "gasLimit": utils.toString(options.gasLimit),
-        "contract": options.contract,
-        "binary": options.binary
-    };
+    var params = new Transaction(options).toPlainObject();
     return this._sendRequest("post", "/transaction", params);
 };
 
@@ -228,16 +220,7 @@ Admin.prototype.signHash = function (options) {
  */
 Admin.prototype.signTransactionWithPassphrase = function (options) {
     options = utils.argumentsToObject(['from', 'to', 'value', 'nonce', 'gasPrice', 'gasLimit', 'contract', 'binary', 'passphrase'], arguments);
-    var tx = {
-        "from": options.from,
-        "to": options.to,
-        "value": utils.toString(options.value),
-        "nonce": options.nonce,
-        "gasPrice": utils.toString(options.gasPrice),
-        "gasLimit": utils.toString(options.gasLimit),
-        "contract": options.contract,
-        "binary": options.binary
-    };
+    var tx = new Transaction(options).toPlainObject();
     var params = {
         "transaction": tx,
         "passphrase": options.passphrase
@@ -270,16 +253,7 @@ Admin.prototype.signTransactionWithPassphrase = function (options) {
  */
 Admin.prototype.sendTransactionWithPassphrase = function (options) {
     options = utils.argumentsToObject(['from', 'to', 'value', 'nonce', 'gasPrice', 'gasLimit', 'contract', 'binary', 'passphrase'], arguments);
-    var tx = {
-        "from": options.from,
-        "to": options.to,
-        "value": utils.toString(options.value),
-        "nonce": options.nonce,
-        "gasPrice": utils.toString(options.gasPrice),
-        "gasLimit": utils.toString(options.gasLimit),
-        "contract": options.contract,
-        "binary": options.binary
-    };
+    var tx = new Transaction(options).toPlainObject();
     var params = {
         "transaction": tx,
         "passphrase": options.passphrase
diff --git a/lib/api.js b/lib/api.js
index 622c1c7..394866d 100644
--- a/lib/api.js
+++ b/lib/api.js
@@ -2,6 +2,7 @@
 "use strict";
 
 var utils = require('./utils/utils.js');
+var Transaction = require("./transaction.js");
 
 /**
  * User API constructor.
@@ -113,15 +114,7 @@ API.prototype.getAccountState = function (options) {
  */
 API.prototype.call = function (options) {
     options = utils.argumentsToObject(['from', 'to', 'value', 'nonce', 'gasPrice', 'gasLimit', 'contract'], arguments);
-    var params = {
-        "from": options.from,
-        "to": options.to,
-        "value": utils.toString(options.value),
-        "nonce": options.nonce,
-        "gasPrice": utils.toString(options.gasPrice),
-        "gasLimit": utils.toString(options.gasLimit),
-        "contract": options.contract
-    };
+    var params = new Transaction(options).toPlainObject();
     return this._sendRequest("post", "/call", params);
 };
 
@@ -302,16 +295,7 @@ API.prototype.gasPrice = function () {
  */
 API.prototype.estimateGas = function (options) {
     options = utils.argumentsToObject(['from', 'to', 'value', 'nonce', 'gasPrice', 'gasLimit', 'contract', 'binary'], arguments);
-    var params = {
-        "from": options.from,
-        "to": options.to,
-        "value": utils.toString(options.value),
-        "nonce": options.nonce,
-        "gasPrice": utils.toString(options.gasPrice),
-        "gasLimit": utils.toString(options.gasLimit),
-        "contract": options.contract,
-        "binary": options.binary
-    };
+    var params = new Transaction(options).toPlainObject();
     return this._sendRequest("post", "/estimateGas", params);
 };
 
diff --git a/lib/transaction.js b/lib/transaction.js
index 7b11bf1..fecbfb2 100644
--- a/lib/transaction.js
+++ b/lib/transaction.js
@@ -262,10 +262,10 @@ Transaction.prototype = {
      *    gasLimit: 2000000
      * });
      * txData = tx.toPlainObject();
-     * // {chainID: 1001, from: "n1USdDKeZXQYubA44W2ZVUdW1cjiJuqswxp", to: "n1SAeQRVn33bamxN4ehWUT7JGdxipwn8b17", value: 1000000000000000000, nonce: 1, …}
+     * // {chainID: 1001, from: "n1USdDKeZXQYubA44W2ZVUdW1cjiJuqswxp", to: "n1SAeQRVn33bamxN4ehWUT7JGdxipwn8b17", value: "1000000000000000000", nonce: 1, …}
      */
     toPlainObject: function() {
-        return {
+        var resObj = {
             chainID: this.chainID,
             from: this.from.getAddressString(),
             to: this.to.getAddressString(),
@@ -275,6 +275,12 @@ Transaction.prototype = {
             gasLimit: utils.isBigNumber(this.gasLimit) ? this.gasLimit.toNumber() : this.gasLimit,
             contract: this.contract
         };
+
+        resObj.value = utils.toString(resObj.value);
+        resObj.gasPrice = utils.toString(resObj.gasPrice);
+        resObj.gasLimit = utils.toString(resObj.gasLimit);
+
+        return resObj
     },
     /**
      * Convert transaction to JSON string.