The stability of slopes under intermittent heavy rainfall is studied. The soil above the wetting front is subjected to dry-wet cycles under intermittent heavy rainfall. Considering the influence of dry-wet cycles on the soil permeability and soil-water characteristics of slope，the traditional Green-Ampt infiltration (GA) model is improved. The expression of slope stability coefficient under intermittent heavy rainfall is established considering the deterioration of dry-wet cycles on soil strength. For slopes without considering intermittent heavy rainfall，the improved GA model can be simplified to the traditional GA model，which indicates that the traditional GA model is a special case of the improved GA model. The results obtained by using the improved GA model and the stability evaluation method are basically consistent with the actual engineering situation，which proves the reliability of the method. According to the variation characteristics of rainfall infiltration rate，the rainfall process can be divided into three stages: stable stage，continuous reduction stage and mutation stage. The slope infiltration depth and instability time of traditional GA are obviously behind that of the improved GA model. Compared with the improved GA model，the traditional GA model which only improves the stability evaluation method is consistent in the instability depth and delayed in the instability time.