The geological conditions of the marine Leikoupo Formation in Western Sichuan are complex, which are mainly manifested as fracture development, fracture strike disorder, formation fragmentation, etc. In order to solve the problems such as wellbore instability, block sticking, and resistance of electric logging, etc. , the technical countermeasures of ultra deep well drilling fluid anti sloughing are proposed by analyzing the engineering geological characteristics of Leikoupo Formation, and the anti collapse drilling fluid system of marine facies in Western Sichuan is constructed. According to the laboratory evaluation, the drilling fluid of this system has strong ability of temperature resistance, pollution resistance and plugging inhibition. The field application shows that drilling, coring, electrical logging and completion operations are smooth. Compared with the previous construction wells, the average ROP is increased by 39. 9% , the average drilling cycle is shortened by 22. 6% , and the average pure drilling rate is increased by 11 . 6% . There is no complex phenomenon such as wellbore instability in adjacent wells, which is of great significance to accelerate the exploration and development process of marine ultra deep wells in Western Sichuan.