To reveal the effect of surface roughness on elastoplastic contact performances for a deep groove ball bearing, the contact between the rolling element and inner raceway is reduced as the extremum problem of a quadratic function based on the load distribution of this kind of bearings. The elastoplastic contact model for a rough deep groove ball bearing is modeled, and solved with the proposed semi-analytical method so as to obtain the elastoplastic contact performance for the bearing. Numerical results show that the surface roughness yields decrements in the pressure peaks at the two contact endpoints along the inner raceway's width direction. Meanwhile, the maximum contact pressure, von Mises stress, and residual stress and deformation for the inner raceway are all larger than the corresponding values for the smooth situation. Moreover, the roughness also causes fluctuating distributions of contact pressure and residual deformation, and brings out a stress concentration at the inner raceway's subsurface, which can lead to a decay of the bearing lifetime.