Formation lithology is the material basis of landslide. In order to more clearly understand the influence of semi-diagenetic microstructure on macroscopic physical and mechanical properties, through the investigation and analysis of '8.21' Zhonghaicun landslide, it is shown that compared with the semi-diagenetic Xigeda Formation with low water content, the particle morphology of high water content tends to be more orderly, but the particle arrangement is more disordered, indicating that the structural stability is worse, and the semi-diagenetic Xigeda Formation is more likely to slide. The grey correlation analysis method was used to study the correlation between the macroscopic strength characteristic parameters and the microstructure parameters of the semi-diagenetic Xigeda Formation in Hanyuan. It was found that the average diameter of the particles had the greatest influence on the cohesion C and the internal friction angle φ. With the increase of water content, the contact of semi-diagenetic microscopic particles in Xigeda Formation is discontinuous, the pores between particles increase, the structure changes greatly, and the overall compactness decreases, which leads to the decrease of semi-diagenetic strength of Xigeda Formation and makes landslide more likely to occur.