Laser generated ultrasonic waves is numerically simulated by mass spring lattice model by considering the laser illumination as a vertical force, which is valid in the ablation regime. Few surface acoustic wave modes including surface skimming longitudinal wave, surface skimming shear wave, and Rayleigh-like wave are recorded in aluminum and copper plates. The results indicate that the excitation efficiency of ultrasound in aluminum plate is higher than that in copper plate. The normal component of the displacement at the epicenter has only the longitudinal wave mode and the shear wave mode appears wthen the detection position has a deviation from the epicenter. In addition, the amplitude increases and the arrive time delays with the deviation distance.