Abstract: Aiming at the problem of mining rate influencing the hard roof breaking step of fully-mechanized caving face in the 2301 thick coal seam in Xinjiang Panjin Coal Mine, based on the field observations and theoretical analysis, we studied the mechanism of mining rate influencing hard roof breaking step through analyzing the structure of hard roof that supported by the top-coal. The results show that the top coal compresses the key layer of overlying basic roof during the fully mechanized caving of hard roof thick coal seam, and when the recovery rate of thick coal seam increases, the supporting force under the key layer of the basic roof will decrease obviously, which makes the working face show the feature of decreasing the break step of roof. When the ratio n of thick coal seam thickness to hard roof thickness is greater and the ratio m of strength is smaller, the influence of the recovery rate of thick coal seam on the fracture step of hard roof is more obvious.