Based on the finite element method of the saturated-unsaturated seepage, the saturated-unsaturated transient seepage field is simulated under the condition of rainfall, and the influence of rainfall intensity, rainfall duration and saturated permeability coefficient on the matric suction of the unsaturated slope is also analyzed completely. The results show that the matric suction is lose on account of the rainwater infiltration; there is no marked influence of the rainfall intensity on variation of matric suction of slope with high saturated permeability coefficient.