Abstract: The fracture of the key strata in the roof of coal seam will lead to the strong mining pressure, especially the hard and thick sandstone layer in the coal seam roof as the main key stratum, its breakage easily leads to mine power disaster. In view of the overlying characteristics of thick sandstone on the roof of a working face, the key strata theory is used to analyze the ultimate step, periodic caving step distance and the corresponding support resistance requirements in the primary fracture of the rock beam. In order to enable the working face supports to bear roof pressure, the pre-splitting blasting measure of the advanced deep hole is used every 20 m before the cut hole. The measured results of mine pressure show that the forced roof caving of thick sandstone can slow down the effect of roof load on the support and realize the safe mining under the existing supporting equipment.