Abstract: Hydraulic fracturing has been extensively used for solving issues caused by strong rock layers above longwall coal panel. The related mechanism of mining-induced stress relief is not well understood. In this paper,a numerical study is performed using the hybrid finite/discrete element code ELFEN to investigate the effect of strong roof layers on mining-induced stress. It is found that hydraulic fracturing can reduce the integrity of the strong rock layers so that they can collapse timely as the longwall face moves ahead. The collapse of localized immediate roof may not substantially affect front abutment pressures. Continuous collapse of the immediate roof can cause timely fracture and collapse of the overlying main roof layers,affecting the large structure of the overburden in the stope,and thus affecting the distribution of mining-induced stress. Continuous hydraulic fracturing of the rock layers above longwall panel can reduce the distance of initial roof collapse and the distance of periodic collapse.