What is the best way to get to Mianshan Mountain from Beijing or Xi'an?

You could take train directly to Jiexiu city and then take a taxi or bus to Mianshan Mountain Scenic area which is around 20km from Jiexiu city center. Several trains are available either from Beijing or Xian to Jiexiu. But Xian is closer, since it takes around 8hrs by train to Jiexiu.