According to the geological conditions of Mabao Coal Mine in Shanxi Province, the width range of the coal pillar of the heading roadway is 6.48~8.97 m calculated by the limit equilibrium theory and the internal and external stress field theory. By using FLAC3D, the vertical stress and plastic zone distribution of coal pillar and the deformation of surrounding rock of roadway were simulated when the width of coal pillar is 5~9 m. The results show that with the increase of coal pillar width, the peak stress and plastic zone range of coal pillar decrease continuously. After the width of coal pillar reaches 7 m, the peak stress reduction trend and plastic zone change are not obvious, and the surrounding rock deformation gradually tends to be stable, in consideration of safe mining and efficient utilization of resources, the width of coal pillar is finally determined to be 7 m. By simulating the stress changes at different positions of the coal pillar in the process of mining, it is determined that the influence range of mining and excavation is 30 to -30 m at the same time. Combined with the deformation of surrounding rock at different positions of the 15202 transportation gateway, a reasonable subsection support scheme is given.