Laser shock processing (LSP) is a new surface modification technology that can improve mechanical properties and extending fatigue life. The numerical simulation was utilized in this work, the IN718 alloy was treated by Gaussian mode laser with the laser pulse energy of 3−7 J, laser pulse width of 12 ns and laser spot in diameter of 3 mm. And the effects of laser pulse energy on the surface morphology and residual stress field of material was investigated. The numerical simulation results showed that after the treatment of LSP, the plastic deformation and compressive residual stress layer with a certain depth is formed on the near surface of material. The amount of the plasticity deformation of material was increased with the laser pulse energy. And the compressive residual stress in surface and the direction of depth are increased with the laser pulse energy too. With the laser pulse energy from 3−7 J, the maximum compressive residual stresses are appeared at the center of the surface corresponding to the laser spot. When the laser pulse energy is increased from 3 J–7 J, the plastic deformation in depth is increases from 0.50 μm–1.86 μm, and the maximum compressive residual stress is increased fromt 362 MPa–742 MPa. In conclusion, LSP can improve mechanical properties of IN718 significantly, and the laser pulse energy is the most important factor to affect the LSP effect. This work can provide a certain theoretical guidance for researchers to study the IN718 alloy treated by LSP.