Landslide disaster is the main geological disaster faced by China at present, and rainfall is an important factor to induce slope instability. The model tests of rainfall and slope toe immersion on gravel soil slope with 10%, 20% and 40% gravel contents were conducted. The soil and water parameters of gravel soil slope were tested by volume moisture sensor and suction sensor. The development processes of wetting front of slope were observed. The displacement and deformation characteristics of slope were studied by PIV technology. By controlling water level and loading conditions, the law of settlement and deformation of soil slope under slope toe immersion was studied. The results showed that under rainfall condition, the higher the gravel content was, the slower the erosion development of the slope surface was, the easier the fine-grained soil of the slope to reach full saturation state was; after slope soil was saturated, the strength decrease of slope soil with 20% gravel content was the most, and the slope was most likely to have the disposable integral damage; the surface of soil slope with 40% gravel content was destroyed first, then the slope shoulder began to slide, which caused the large-scale sliding failure of the whole slope; the soil slope with 10% gravel content was mainly eroded and deformed in slope surface; slope erosion and deformation were the main variation of soil slope with 10% gravel content, less prone to overall damage. During the immersion of slope toe, the higher the gravel content were, the smaller the deformation of the slope was, the better the drainage characteristics of the slope was, and the faster the matrix suction recovery was during the water level decline; the lower the gravel content was, the larger the suction loss range of the slope was in the process of slope toe immersion. Under the action of slope toe immersion and slope top loading, soil slope with 20% gravel content was most vulnerable to failure; soil slope with 10% gravel content would produce large deformation; soil slope with 40% gravel content had good stability.