Rainfall is one of the most important factors to induce landslides. The erosion and infiltration of rainwater on the slope during rainfall will significantly reduce its structural stability, which will easily lead to slope failure. In this study, the main factors and influence rules of subgrade slope water damage are found out by combining with slope model test and GeoStudio (slope / W and seep / W coupling) program in order to simulate the effect of rainfall on subgrade slope under the specific soil quality, compaction degree and erosion infiltration time control conditions. The results show that: in the process of rainfall, the external structure of the slope is damaged due to the erosion of the slope surface by rainwater, while the internal structure of the slope is reduced due to the infiltration of rainwater, and both of them act simultaneously from the outside to the inside, resulting in the overall failure of the slope; With the compactness of the two kinds of soil slopes increased from 85% to 95%, the erosion volume of sandy soil slope decreased by 46.18%, and the internal safety factor of the slope increased by 13.74%, while the erosion volume of cohesive soil slope decreased by 33.7%, and the safety factor increased by 10.21%; With the increase of rainfall time, the scour depth of cohesive soil slope tends to be stable, while that of sandy soil slope tends to increase. The overall safety factors of cohesive soil slope and sandy soil slope decrease by 26.32% and 32.87% respectively; Under the same control conditions, the water damage resistance and overall stability of cohesive soil slope are better than that of sandy soil slope.