Tube well dewatering is widely used in the construction of underground works for its high drainage efficiency with simple equipment. This paper studied the scheme optimization of the tube well dewatering of a foundation pit by river and analyzed the key and difficult points in the dewatering process in high altitude area based on the constructin practice of dewatering project by river in Lhasa and with the reference of the actual construction effects and the actual construction conditions. As the dewatering scheme is more scientific, the dewatering efficiency is also improved.