During the excavation of a wharf yard in northern Sichuan，the soil slope at the back edge cracked and deformed，and quickly slid along the top of the bedrock to form a landslide. Then the soil above the back edge of the landslide formed two-stage arc deformation cracks due to the traction of the landslide. In this paper，starting from the terrain changes before the landslide，the characteristics of the sliding surface and the cracks at the back edge after the landslide，on the basis of the original survey data，combined with field investigation and pit exploration，the sliding mechanism，stable state and treatment measures of the landslide are studied by using the method of limit equilibrium mechanics analysis. It is concluded that the main internal cause of landslide is that the water content of soil near the foundation cover interface is too high and its shear strength is too low. After the free face formed by construction excavation，the shear stress concentration near the foundation cover interface exceeds the shear strength of soil，inducing landslide，and the corresponding treatment measures are proposed.