Abstract: To meet the requirements for drilling fluid used in complex interval of Weixi block, based on drilling phenomenon of directional well, the application results of potassium chloride/polyglycol drilling fluid system is analyzed for directional well in Weixi block. The study results show that potassium chloride/polyglycol drilling fluid system can meet basically the requirements for drilling directional well in Weixi block. However, the wellbore collapse problem from Wei-2 to Liu-2 Members has not solved completely. Further study and optimization should been conducted to solve complex well borehole collapse problem, and ensure the subsequent operation safety of directional wells and horizontal wells.