Abstract: At present, oil-based drilling fluids are commonly used in the drilling process of shale gas, but there are a series of environmental problems of oil-based drilling fluids. Therefore, it is necessary to develop an efficient and environmental friendly water-based drilling fluid system which can replace oil-based drilling fluid. In this paper, aiming at the actual situation of shale gas strata in Longmaxi-Wufeng Formation of Fuling reef dam block, the experiments, such as rheological property, high temperature expansion rate, rolling recovery rate, normal temperature medium pressure water loss, high temperature high pressure water loss and extreme pressure lubrication friction coefficient were carried out before and after aging, then using KCl and sodium formate as inhibitors, compounding quasi-nano-particles with the new soltex, and compounding efficient lubricant with emulsifier compound, a efficient environment-friendly water base drilling fluid system with strong inhibitory, strong sealing and good lubrication was developed. The performance evaluation results show that the expansion rate is 5.12%, FL (API) = 1.6 mL, FL (HTHP) = 4.8 mL, K_f = 0.14, which can meet the requirement of horizontal shale formation drilling.