In order to solve the problems of environmental protection and high cost of drilling fluid treatment caused by the application of oil-based drilling fluid in shale gas horizontal wells, plugging agents, inhibitors and lubricants with excellent performance were selected through laboratory experiments, and an anti-sloughing water-based drilling fluid system suitable for shale gas horizontal wells was developed in combination with other treatment agents, and its comprehensive performance was evaluated in the laboratory. The results show that after aging at 130 ℃, the rheological property of the drilling fluid system is stable, the filtration capacity is small, and it has good temperature resistance; the instantaneous filtration rates and static filtration rates of the plugging experiment of the low permeability sand pan of the drilling fluid system are 0.6 mL and 0.33 mL/min, respectively, which have good plugging performance; the inhibition and lubrication performance of the drilling fluid system are basically the same as that of the field oil-based drilling fluid system In addition, when 20%NaCl, 2%CaCl2 and 20% cuttings are added into the drilling fluid system, the rheological properties and filtration capacity of the system before and after aging do not change much, indicating that the system has strong anti-pollution ability. The field application results show that the drilling process of well X-101 using the new anti-sloughing water-based drilling fluid is smooth, all construction parameters meet the design requirements, and compared with the previously drilled well x-3hm, the drilling cycle, downhole complex time and average well diameter expansion rate are significantly reduced, and the drilling speed in the horizontal section is significantly improved, achieving good drilling results.