Abstract: Stability of support is a core factor affecting the safety performance and productivity of longwall comprehensive mechanized top coal caving mining technology in large inclination coal seam.Taking 5105 synthesized working face of Pulongwan Coal Mine as the research background, numerical simulation and engineering validation were used to analyze the mechanism of top coal damage, dynamic transportation law and its influence on the stability of the support under the action of non-equilibrium load and complex constraint conditions.The results show that the inclination angle of the coal seam is a key factor affecting the mechanical behavior of the top coal, and along the tendency direction of the working face, from low to high, the crushed area and the plastic deformation area gradually expand, and its bearing and load transfer efficiency gradually weaken, resulting in the reduction of the working resistance of the support.In the lower part of the working face tendency, the broken top coal helps to stabilize the composite structure of “top coal-support-floor” because of the physical barrier effect of gangue in the mining area.In the middle and high part of the working face tendency, the top coal fragments tend to move towards the direction of the tail beam of the support after losing the gangue constraints, destabilizing the system of “top coal-support-floor” and decreasing its overall stability.