Abstract: There are abundant wind energy resources in Northwest China, but the cost of wind farm construction increases due to the treatment of loess collapsible under overburden pressure in this area. Exploring the optimization scheme of WTG foundation in collapsible loess area has great significance to the development of wind energy. In this paper, the infiltration process of rain fall in loess is simulated using finite element method with unsaturated soil, and the range and location of the water-resisting layer are determined using the simulation results. Then the replacement thickness is determined according to different collapsibility coefficients to meet the requirements of bearing capacity and collapsibility. The replacement schemes under different collapsibility coefficients are obtained. The optimization scheme can both ensure safety and save the cost of wind farm. Since the Ningxia wind farm has been built three years, the test results show that the optimized scheme is safe and reliable.