In order to evaluate the impact of rainfall infiltration on slope stability, a project slope in southwest China is selected for the simulation. According to the actual rainfall conditions in the area, GeoStudio and other softwares are used to establish the model and select the parameters. The slope stability considering rainfall duration, intensity, main rainfall types and early rainfall is analyzed by finite element method. The results show that short-term heavy rainfall will cause the slope stability to decline sharply in a short time, which will pose a great threat to the safety of the slope; the safety coefficient of slope is affected by the lag of rainfall infiltration. Then the sensitivity of influencing factors of slope stability are compared and analyzed by single factor analysis method, and the sensitivity relationship between different influencing factors of different rock and soil layers is obtained, which is of a certain referential value for slope stability analysis in practical engineering.