Shot peening improves the fatigue resistance of the workpiece by introducing residual compressive stress. As an important factor in shot peening process control, shot peening coverage significantly affects the residual stress and surface roughness of gears. However, the current research has paid little attention to the correlation between shot peening coverage and gear residual stress and surface roughness. Aiming at this problem, a simulation model for aircraft gear shot peening strengthening based on discrete element model (DEM) and finite element model (FEM) coupling was established. The influence of shot peening coverage on gear residual stress and surface roughness was studied through theoretical simulation and experimental verification. The results show that with the increase of coverage, the gear surface roughness S_a increases rapidly initially and then decreases gradually, when the coverage exceeds 200%, the surface roughness starts to decrease; The coverage has no significant effect on the residual compressive stress value and the depth of the residual compressive stress on the tooth surface, but has a greater effect on the maximum residual compressive stress. Maximum residual compressive stress increases significantly with the increase of the coverage, but the increase rate decreases when the coverage exceeds 300%; Along the tooth profile, the residual compressive stress exhibits the maximum value at the tooth root, and the position closer to the top of the tooth is smaller. This is because the collision probability between the projectile flow and the tooth surface increases as the position approaches the tooth root, and the higher number of impacts leads to greater compressive stress on the tooth surface.