Abstract: Using a modified damage function model with the percolation-relaxation function, the spallation in nanocrystalline copper by laser irradiation loading was investigated numerically. Laser-driven loadings were simulated by a Gaussian temporal pressure profile, applied at the front surface of the Ni alloy substrate. Simulation results indicated that the damage evolution had serious influence on the wave propagation in nanocrystalline copper sample. Good agreement was obtained between experimental and predicted free surface velocity profiles, which confirmed the capability of the damage model for describing the spallation process in nanocrystalline copper.