Based on the numerical simulation of laser shock peening (LSP) process of oxygen-free high-conductivity (OFHC) copper, the effect of numbers of repetitive peens on the residual stress field and the dimple in the LSP process is studied, and the mechanism of strengthening residual stress is discussed emphatically. The numerical results show that, with the increase of numbers of repetitive peens, both the plastic deformation of target materials and the dimple depth increase, and both the residual stress and the flow stress of target materials gradually approach to saturation. Compared with those by the third or fourth LSP, the influence on the size and distribution of the residual stress induced by the second LSP is more significant. The strengthening of the residual stress after repetitive LSPs is mainly attributed to the hardening history of target materials, and the residual stress induced by the previous LSP shows certain inhibition effect on the material hardening in the current LSP process.