In order to detect the crack information by laser ultrasonic technology,based on the thermo-solid coupling physics field of finite element analysis software (COMSOL),a laser ultrasonic non-destructive testing model is established.The laser is equivalent to the surface force source from the power density,spatial distribution and time distribution of the laser.Force source,the perfect matching layer,low reflection boundary,thermal insulation boundary are used to eliminate boundary echo.By fixing the distance between the excitation source and the probe and analyzing the probe signal,the simulation of the influence of cracks on the pulse echo peak and arrival time at different positions is carried out.Compared with the experiment,the model has high correctness.The results show that the distance between the fixed excitation source and the probe,the peak value of the pulse echo will increase as the distance between the crack and the probe decreases,and the arrival time of the pulse echo will gradually advance;the amplitude of the transmitted wave will attenuate and the arrival time will be slightly delayed.