In the initial mining stage of fully mechanized top coal caving face with hard roof in thick coal seam, the top coal caving is poor and the roof caving is not timely, which threatens the safe production of the working face. No.1521 Face of Chaigou Mine was taken as the engineering background, the problems existing in the mining of the working face were analyzed, the strength of the top coal and roof strata was measured, and the technical scheme of hydraulic fracturing and roof cutting was put forward. The mechanical model was established, and the stress state around the roof cutting borehole was analyzed. On this basis, the main parameters such as roof cutting height, borehole length and water injection pressure were calculated. In order to ensure the fracturing effect, two methods of shallow hole drilling and deep hole directional long distance bedding were used for staged fracturing. Field application showed that after fracturing, the proportion of coal blocks with equivalent diameter below 1.2 m of top coal block increased from 70 % to 92 %, which promoted the caving of top coal and increased the recovery rate of coal resources from 81 % to 86 %. The mine pressure of the working face in the roof cutting area was gentle, the dynamic load coefficient and stress concentration coefficient of the support were reduced, and the pressure relief effect was obvious.