In order to study the relationship of the bedrock thickness with surface movement and surface subsidence coefficient on large cutting height fully mechanized top coal caving mining under thick alluvium,we built the numericalstimulation models for large cutting height fully mechanized top coal caving mining under specific geological and mining conditions of a certain coal mine by using the software FLAC3D.Using the newly built model,we performed the numerical simulation and obtained the isoline maps for surface subsidence and horizontal movement under different thickness of bedrock.In addition,we made the regression analysis to obtain the corresponding curves and their relational expressions.The results show that 1) the surface subsidence coefficient(q) decrease with the increase of the ratio of bedrock thickness(H-h) to the mining depth(H),and increase with the increase of the ratio of mining thickness(m) to the bedrock thickness,2) the surface subsidence(W) and horizontal movement range(U) decrease with the increase of the ratio of bedrock thickness,and3) on bedrock is relatively thin area,alluvium produce field disturbance compression by the influence of mining,this is another reason lead to surface subsidence bnormal.These conclusions can meet engineering requirements according to the field case study.