Abstract: The highway slope of K48+722~800 in Jinping hydropower station is greatly affected by rainfall. The deep stability of this slope is related to the safety of the station project. On the basis of the experimental data, this paper uses Fredlund-Xing method to fit the SWCCs of the slope soils. The volumetric water content is used to represent the initial moist station of the soil. Then the evolution rules of pressure head, the influence of volumetric water content on pressure head and slope stability under rainfall conditions are researched numerically. The results show that, the pressure head at the slope surface and slip increases gradually at early rains. Then the area with increasing pressure head can expend toward the inside of slope body. For a period of time after rainfall, the pressure head of the slope surface and inferior region dissipates, while the pressure head of partial trailing area of slip increases. The pressure head would increase with the volumetric water content. And when the volumetric water content is little, the stability coefficient of slope can keep unchanging for a certain time and then slowly decreases. However, when volumetric water content increases, the stability coefficient of the slope can have an upward trend after rainfall.