Due to the diversity of geological conditions， distributed in complex formation such as loose and broken formation， high stress formation， faults broken zone in the Qinghai-Tibet Plateau. In geological drilling， we often suffer problems such as hole collapse， slurry leakage， diameter reduction， stuck drill， buried drill， etc. At the same time， the mud cake formed by the mud is thin， the cementing ability is poor， and the rock carrying ability is weak. Therefore， flushing fluid is the key to achieve drilling smoothly in complex formation. Combining the geological characteristics of the complex formation of the Qinghai-Tibet Plateau， developed a new flushing fluid for low solid phase polymers. The flushing fluid based on sodium bentonite and additives such as micro foaming agent， etc. It has the characteristics of good fluidity， strong cementation， and moderate water loss， suitable for use in geological drilling of complex formation in the Qinghai-Tibet Plateau.