We present a case study of antecedent rainfall-induced failure of engineering slope. The impact of pore-water pressure, the increment of pore-water pressure, and water content, the factor of safety are investigated by numerical models for an actual slope in Yunnan, China. The results indicate that antecedent rainfall played an important role in the stability of the slope. The model reasonably explains the time lag between the occurrence of rainfall and landslides. Pore-water pressures have significantly changed at the upper layer of red clay slope, the cracks phenomenon at the upper of the slope agrees with the field observations before landslide. The saturated zone of the slope gradually expands from the top to bottom of the slope, the major reason for landslide is that the surface stagnant water after rainfall gradually infiltrates into the weathered gneiss rock, resulting in the decrease of the strength of weathered gneiss rock, and then the weight of later rainfall caused the landslide of the slope. The factor of safety of the slope was evaluated by the modified limit equilibrium methods, it was shown that the actual failure occurred when the calculated factor of safety approaches its minimum 0.97. The landslide is characterized by shallow landslides.