Is there any way we could go the TAR by Train?

Yes, the Qinghai-Tibet (Qingzang) Railway from Golmud to Lhasa started operating in July 2006. The journey all the way from Beijing takes just under 48 hours. Trains to Lhasa originate in Beijing, Xining, Lanzhou, Shanghai, Guangzhou, Chongqing and Chengdu.