Abstract: Thick coal seams are an important part of China's coal resources, but the stability of the overlying rock during mining poses a challenge to mine safety and effective resource recovery. This study, based on the 1109 working face of a coal mine in Shandong Province, China, uses the FLAC 3D numerical simulation technology to investigate the movement of overlying rock under underground coal pillar mining with thick coal seams. The simulation results show that during mining, the boundary coal pillars on both sides of the mined area are in a state of stress concentration, and the degree of stress concentration increases as the working face advances. The filling body area shows a stress reduction zone, forming a pressure arch with a filling step range, effectively releasing the pressure on the roof and reducing the risk of roof collapse. When the coal seam is mined in layers from below, due to the release of roof stress to a certain extent during the upper layer mining, the roof subsidence is less than that of the upper layer; at the same time, as the filling rate increases, the stress carried by the boundary coal pillars on both sides of the working face gradually increases, while the area of the pressure reduction zone in the filling body area gradually decreases. According to the engineering geological conditions of the working face, when the filling rate is greater than or equal to 90%, both effective control of surface deformation and mining efficiency can be achieved.