private static string GetUnityPath()
  {
    #region 通过注册便获取Unity安装路径
    var regKey = @"Unity package file\DefaultIcon";
    RegistryKey registryKey = Registry.ClassesRoot.OpenSubKey(regKey);
    string pathName = (string)registryKey.GetValue(null); // "(Default)" 
    if (string.IsNullOrEmpty(pathName))
    {
      return null;
    }
    int index = pathName.LastIndexOf(",");
    if (index != -1)
    {
      var exepath = pathName.Substring(0, index).Replace("\"", string.Empty);
      var binpath = Path.GetDirectoryName(exepath); 
      var di = new DirectoryInfo(binpath);
      if (di.Parent != null)
      {
        return di.Parent.FullName;
      }
    }
    return null;  
    #endregion
  }

static void StartPeocess(string applicationPath)
{
  Process po = new Process();
  po.StartInfo.FileName = applicationPath;
  po.Start();
}

string[] args = unityPath.Split('\\');
Process[] pro = Process.GetProcessesByName(args[args.Length - 1].Split('.')[0]);//Unity
foreach (var item in pro)
{
  UnityEngine.Debug.Log(item.MainModule);
  item.Kill();
}

using Microsoft.Win32;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using UnityEditor;
using UnityEngine;

public class ReStartUnityTools : MonoBehaviour
{
  public static string UnityExePath = "E:\\Unity 5.5.2\\Unity\\Editor\\Unity.exe";

  [MenuItem("Tools/ReStartUnity(重启Unity)")]
  public static void ReStartUnity()
  {
    string unityPath = UnityExePath;// GetUnityPath();公司电脑通过注册表是可以的，家里电脑不行，你们可以用这个函数试下，实在不行先写上Unity安装路径吧

    StartPeocess(unityPath);
    string[] args = unityPath.Split('\\');
    Process[] pro = Process.GetProcessesByName(args[args.Length - 1].Split('.')[0]);//Unity
    foreach (var item in pro)
    {
      UnityEngine.Debug.Log(item.MainModule);
      item.Kill();
    }
  }

  private static string GetUnityPath()
  {
    #region 通过注册便获取Unity安装路径
    var regKey = @"Unity package file\DefaultIcon";
    RegistryKey registryKey = Registry.ClassesRoot.OpenSubKey(regKey);
    string pathName = (string)registryKey.GetValue(null); // "(Default)" 
    if (string.IsNullOrEmpty(pathName))
    {
      return null;
    }
    int index = pathName.LastIndexOf(",");
    if (index != -1)
    {
      var exepath = pathName.Substring(0, index).Replace("\"", string.Empty);
      var binpath = Path.GetDirectoryName(exepath);  // 
      var di = new DirectoryInfo(binpath);
      if (di.Parent != null)
      {
        return di.Parent.FullName;
      }
    }
    return null;  
    #endregion
  }

  static void StartPeocess(string applicationPath)
  {
    Process po = new Process();
    po.StartInfo.FileName = applicationPath;
    po.Start();
  }
}