Abstract: On the basis of saturated-unsaturated seepage model, by simulating transient seepage fields due to rainfall infiltration for Beijing Olympic Park Hill, the matric suction in the slope is analyzed. By the extendedMohr-Coulomb failure criterion, the slope stability is analyzed using limit equilibrium method. Therefore the factors of safety at different time during the rainfall are calculated. In addition, effects of different rainfall model on seepage fields distribution of unsaturated soil slope and the slope stability are analyzed in this paper. Then, the reliability of slope stability as the soil parameters varying is presented by means of probability method.