Abstract: In order to explore the characteristics of surface defects of coated cylindrical parts and laser ultrasonic surface wave, a numerical model of coated cylindrical parts was established based on the finite element method.The relationship between coating,surface defect depth and laser ultrasonic surface wave was analyzed by numerical simulation.The results show that:the existence of the coating will cause the dispersion on the coated cylindrical surface, and the dispersion is related to the thickness of coating; when there is a crack on the surface, characteristic peaks RR and RS can be found in the reflective surface Rayleigh wave, and there is a phased linear relationship among the time difference Δt and the depth of the defect, and the demarcation point is related to the coating thickness; the amplitude of the frequency domain waveform of the transmitted signal after the defect also decreases as the depth of the defect increases.