Abstract: The deformation characteristics and mechanism of landslides are crucial for slope stability and slope failure warning. Significant deformation occurred in the retaining wall of a fill slope in Furongjiang Town, Zheng’an County, during the rainy season, with notable development of soil wall cracks. In order to determine the safety status of the slope, geological and hydrological conditions of the slope were investigated, and the characteristics of the retaining wall and surrounding ground cracks were statistically analyzed. The stability of the slope after unsaturated rainfall infiltration was calculated by FLAC^3D. The results are as follows: (1) retaining wall cracks develop along the principal plane of maximum principal stress, and the retaining wall settle symmetrically along the axis of the groove; (2) Through the infiltration analysis of rainfall intensity of 10mm/d (light rain) and 250mm/d (heavy rain), the safety factors of light rain on 8 days and 5 days after rainfall cessation decreased by 14.5% and 4.3%, respectively, and the safety factors of heavy rain on 1 day and 2 days after rainfall cessation decreased by 10% and 3.5%, respectively. (3) The deformation mechanism of the slope was analyzed, indicating that the increase in gravitational force after filling and rainfall led to increased sliding force. Rainfall reduced matric suction and effective stress, resulting in decreased shear strength and sliding resistance of the soil. (4) Based on the characteristics of retaining wall cracks and deformation monitoring results, the main sliding direction, geometric boundaries, and landslide zones of the slope were predicted, and subsequent swelling phenomenon at the forefront of the slope confirmed the accuracy of the landslide identification results.