The surface acoustic wave excited by the laser irradiating the surface of the metal cylinder generates dispersion and phase shift during the propagation along the surface of the cylinder,and the amplitude at the front edge of the surface defect is significantly enhanced,which provides a new way for the detection of surface defects. Based on the phenomenon of surface acoustic wave excited by laser,it is proposed to determine the position of the defect by scanning the detection point,and the formula of calculating the depth of surface defect and the propagation path near the surface defect are given. Numerical research show that:(1) Compared with the pulse echo method,the scanning detection point method improves the position accuracy of the detection of defect,and effectively reduces the influence of the dispersion and frequency shift phenomenon on the position accuracy of surface defects. (2) When the defect depth range is 1~2 mm,the error between the simulated defect depth and the actual defect depth is controlled within 6 % by the given formula of calculating defect depth,and the validity of the proposed formula of calculating defect depth is verified. The above research results provide a valuable reference for applying the surface wave to detect surface defects of cylindrical parts.