Abstract: The anti-sloughing and high temperature-resistant properties of conventional water-based drilling fluids fail to meet the needs of exploration and development of complicated deep wells. To address this issue, surface hydration inhibitors and nano-scale plugging agents were developed. Through the optimization of other treatment agents and ratio optimization, a high temperature-resistant and anti-sloughing water-based drilling fluid system with a density of 2.00 kg/L was formed. The laboratory performance evaluation shows that the temperature resistance of the drilling fluid system reached 220 ℃; the density difference between the upper and lower parts is only 0.02 kg/L after standing for 96 h; the resistance to cutting contaminant is more than 3.0%, and the resistance to calcium chloride pollution is more than 0.6%. Lubrication and inhibition properties are only inferior to oil-based drilling fluid, and the plugging rate of tight sandstone is 85.6%. Field application results show that the drilling fluid system still maintains great borehole purification capacity in high-temperature deep wells, excellent settlement stability, outstanding wellbore stability, and favorable lubrication drag reduction performance. The high temperature-resistant and anti-sloughing water-based drilling fluid system provides technical support for the drilling and completion of deep and ultra-deep wells in complex formations.