Abstract: In order to study the law of surface subsidence for fully-mechanized top coal caving under thick nnconsolidated layers , on the basis of the surface movement observation data of P1501 working face in Poxi coal mine,the effects of fully-mechanized top coal caving on the parameters of surface movement and deformation and dynamic parameters are studied under the condition of thick unconsolidated layers. It was concluded that, compared to general mining geological conditions, the surface subsidence coefficient and horizontal movement coefficient caused by fully mechanized caving mining are more larger under the thick unconsolidated layers, is 0.88 and 0.69 respectively, while the main influence angle tangent, the mining influence propagation angle and the inflection offset are smaller, is 1.71、54.2°and -0.03H0～0.11H0 respectively; The initial period of surface movement is relatively short, and the ratio of total surface movement time is only 9.6%, while the active phase is longer, and the ratio of the total moving time is 50.6%, the ratio of the stage subsidence to the total subsidence is 97.3%.