Abstract: Rainfall has become the main factor increasingly,which influences the stability of loess slope as the groundwater in loess regions exists deeply.According to the theory of saturated-unsaturated seepage and taking the influence of rainfall infiltration into account,under the condition of hundred-year rainfall and based on the finite element method,we carried out numerical simulation for the loess slope of Yanliang-Yumenkou highway.Combined with the experimental results,we concluded that the depth of water infiltration is limited under the strong rainfall,which is about 2 meters under surface layer commonly,and the longer the rain falls,the deeper the water seeps,and the stability coefficient of slope gradually decreases,however,which dose not affect the safety of the whole slope.At the same time surface eroding comes forth,and there will be some part destroying if no any measure is taken,finally leading to the whole failure.As to the old landslide or dangerous slope,the failure frequency becomes in direct proportion to the rainfall intensity,and has certain hysteresis quality.