About 18.8 km. According to Baidu map, the whole driving distance from Tsinghua University to Tiananmen Square is about 18.8km, and it takes about 43 minutes to pass through Xitucheng Road and West Second Ring Road. You can also take Daxing Line of Metro Line 4 first, and then transfer to Metro Line 1. The whole journey takes about 1 hour and 2 minutes.