In order to study on the surface movement law in thick alluvium mining, the numerical model of stope with different thickness alluvium was established by UDEC program, the surface subsidence and movement deformation characteristics of thick alluvium were studied, the effect of different thickness alluvial on surface subsidence was analyzed. The results showed that the surface deformation was divided into three stages: the initial stage, the active stage and the attenuation stage, thick alluvium had shielding, buffering and synergistic coupling effect for surface subsidence, the surface subsidence was larger because the thickness alluvium was larger, but the surface subsidence rate changed little. The condition of thick alluvium had the mitigate effect on the surface subsidence.