Abstract: The optimal roadway height of gob-side entry retaining in thick coal seam is studied by theoretical analysis and numerical simulation under the condition of hard roof in Shaqu Coal Mine. Through theoretical analysis, the roof fracture motion law of gob-side entry retaining in thick coal seam under the condition of hard roof is analyzed. The reasonable mining height (roadway height) was determined to be 4.5 m by numerical simulation. The results show that, when the mining height is 4.5 m, the overall deformation of gob-side entry retaining system is small, the roadway deformation is stable and has a higher effective section, the surrounding rock bearing structure of the roadway is more stable, and the stability of the roadway retaining system is effectively improved. It is proved that there is an optimal roadway height of gob-side entry retaining in thick coal seam under the condition of hard roof.