diff --git a/bin/emulator.js b/bin/emulator.js
index 64388b2..40e125c 100644
--- a/bin/emulator.js
+++ b/bin/emulator.js
@@ -4,7 +4,8 @@
 
 'use strict';
 
-var spawn = require('child_process').spawn;
+var spawn = require('./spawn');
+var threadKill = require('./thread-kill');
 
 /**
  * Emulator
@@ -17,7 +18,7 @@ function Emulator(task){
 
 Emulator.prototype = {
   start: function (){
-    this.thread = this.exec(this.task.command, {
+    this.thread = spawn(this.task.command, {
       env: this.task.env,
       cwd: this.task.cwd
     });
@@ -26,53 +27,17 @@ Emulator.prototype = {
   },
   stop: function (){
     if (this.thread) {
-      this.exec('taskkill /t /f /pid ' + this.thread.pid);
+      var context = this;
 
-      ['stdin', 'stdout', 'stderr'].forEach(function (stream){
-        this.thread[stream].removeAllListeners();
-      }, this);
+      threadKill(this.thread.pid, function (){
+        ['stdin', 'stdout', 'stderr'].forEach(function (stream){
+          context.thread[stream].removeAllListeners();
+        });
 
-      this.thread = null;
+        context.thread = null;
+      });
     }
-  },
-  exec: function (){
-    var parsed = normalizeExecArgs.apply(null, arguments);
-
-    return spawn(parsed.shell, parsed.args, parsed.options);
   }
 };
 
-/**
- * normalize exec args
- * @param command
- * @param options
- * @returns {{cmd: *, shell: *, args: *, options: *}}
- */
-function normalizeExecArgs(command, options){
-  var shell, args;
-
-  // Make a shallow copy before patching so we don't clobber the user's
-  // options object.
-  options = options || {};
-
-  if (process.platform === 'win32') {
-    shell = process.env.comspec || 'cmd.exe';
-    args = ['/s', '/c', '"' + command + '"'];
-    options.windowsVerbatimArguments = true;
-  } else {
-    shell = '/bin/sh';
-    args = ['-c', command];
-  }
-
-  if (options.shell) {
-    shell = options.shell;
-  }
-
-  return {
-    shell: shell,
-    args: args,
-    options: options
-  };
-}
-
 module.exports = Emulator;
diff --git a/bin/spawn.js b/bin/spawn.js
new file mode 100644
index 0000000..6e571b5
--- /dev/null
+++ b/bin/spawn.js
@@ -0,0 +1,49 @@
+/**
+ * Created by nuintun on 2016/1/14.
+ */
+
+'use strict';
+
+var spawn = require('child_process').spawn;
+
+/**
+ * normalize exec args
+ * @param command
+ * @param options
+ * @returns {{cmd: *, shell: *, args: *, options: *}}
+ */
+function normalizeExecArgs(command, options){
+  var shell, args;
+
+  // Make a shallow copy before patching so we don't clobber the user's
+  // options object.
+  options = options || {};
+
+  if (process.platform === 'win32') {
+    shell = process.env.comspec || 'cmd.exe';
+    args = ['/s', '/c', '"' + command + '"'];
+    options.windowsVerbatimArguments = true;
+  } else {
+    shell = '/bin/sh';
+    args = ['-c', command];
+  }
+
+  if (options.shell) {
+    shell = options.shell;
+  }
+
+  return {
+    shell: shell,
+    args: args,
+    options: options
+  };
+}
+
+/**
+ * exec thread
+ */
+module.exports = function (){
+  var parsed = normalizeExecArgs.apply(null, arguments);
+
+  return spawn(parsed.shell, parsed.args, parsed.options);
+};
diff --git a/bin/thread-kill.js b/bin/thread-kill.js
new file mode 100644
index 0000000..cba6c10
--- /dev/null
+++ b/bin/thread-kill.js
@@ -0,0 +1,116 @@
+/**
+ * Created by nuintun on 2016/1/14.
+ */
+
+var spawn = require('./spawn');
+var exec = require('child_process').exec;
+
+/**
+ *
+ * @param pid
+ * @param signal
+ * @param callback
+ */
+module.exports = function (pid, signal, callback){
+  var tree = {};
+  var pidsToProcess = {};
+
+  tree[pid] = [];
+  pidsToProcess[pid] = 1;
+
+  if (typeof signal === 'function') {
+    signal = 'SIGKILL';
+    callback = signal;
+  }
+
+  switch (process.platform) {
+    // win32
+    case 'win32':
+      exec('taskkill /pid ' + pid + ' /T /F', callback);
+      break;
+    // darwin
+    case 'darwin':
+      buildProcessTree(pid, tree, pidsToProcess, function (parentPid){
+        return spawn('pgrep', ['-P', parentPid]);
+      }, function (){
+        killAll(tree, signal, callback);
+      });
+      break;
+    // linux
+    default:
+      buildProcessTree(pid, tree, pidsToProcess, function (parentPid){
+        return spawn('ps', ['-o', 'pid', '--no-headers', '--ppid', parentPid]);
+      }, function (){
+        killAll(tree, signal, callback);
+      });
+      break;
+  }
+};
+
+function killAll(tree, signal, callback){
+  var killed = {};
+
+  try {
+    Object.keys(tree).forEach(function (pid){
+      tree[pid].forEach(function (pidpid){
+        if (!killed[pidpid]) {
+          killPid(pidpid, signal);
+          killed[pidpid] = 1;
+        }
+      });
+      if (!killed[pid]) {
+        killPid(pid, signal);
+        killed[pid] = 1;
+      }
+    });
+  } catch (error) {
+    if (callback) {
+      return callback(error);
+    } else {
+      throw error;
+    }
+  }
+  if (callback) {
+    return callback();
+  }
+}
+
+function killPid(pid, signal){
+  try {
+    process.kill(parseInt(pid, 10), signal);
+  }
+  catch (error) {
+    if (error.code !== 'ESRCH') throw error;
+  }
+}
+
+function buildProcessTree(parentPid, tree, pidsToProcess, spawnChildProcessesList, callback){
+  var allData = '';
+  var ps = spawnChildProcessesList(parentPid);
+
+  ps.stdout.on('data', function (data){
+    allData += data.toString('ascii');
+  });
+
+  var onClose = function (code){
+    delete pidsToProcess[parentPid];
+
+    if (code != 0) {
+      // no more parent processes
+      if (Object.keys(pidsToProcess).length == 0) {
+        callback();
+      }
+      return;
+    }
+
+    allData.match(/\d+/g).forEach(function (pid){
+      pid = parseInt(pid, 10);
+      tree[parentPid].push(pid);
+      tree[pid] = [];
+      pidsToProcess[pid] = 1;
+      buildProcessTree(pid, tree, pidsToProcess, spawnChildProcessesList, callback);
+    });
+  };
+
+  ps.on('close', onClose);
+}
\ No newline at end of file