The surface subsidence caused by mining is closely related to the nature and structure of the overlying strata and soil layer, and the characteristics of mining subsidence under the condition of super-thick alluvium is special. By means of geotechnical test and numerical simulation, the mechanical properties of super-thick alluvium and its influence on the surface subsidence were studied. The shear strength of clayey soil in Jiaozuo mining area were studied through unconsolidated undrained triaxial test, and the range of internal friction angle and cohesion force of clayey soil in Jiaozuo mining area were presented. Taking a panel covered by super-thick alluvium as an example, combined with the triaxial shear test results, the influences of thickness, friction angle and cohesive force of alluvium on the surface subsidence were researched. The results of the numerical simulation were compared with the measured results. The results show that the maximum surface subsidence value increases with the increase of the thickness of alluvium, and decreases with the increase of the friction angle and cohesive force. This paper combines the geotechnical test results of super-thick alluvium mechanical property with the surface subsidence induced by mining, which has a certain guiding significance for the study of the mining subsidence.