In order to carry out the comprehensive planning in Brahmaputra Basin and monographic study on water resources development and conservation, 4 boreholes with depth of 200～300m were laid out in Lilong dam site and Benzong dam site of Brahmaputra main stream. This paper discusses the exploration and hole-building processes in deep overburden layer of alpine region in Tibet based on the successful experience obtained in the above 4 boreholes drilling.