It is able to generate the ultrasonic waves on the surface of materials based on the laser-generated ultrasonic technology which is an important part of non-destructive testing for material defects. With the finite element analysis software of Abaqus, the defect model of the symmetric aluminum to be measured was established based on the laser ultrasonic thermo-elastic mechanism. Besides, the propagation characteristics of the laser-induced surface wave in the material and the interaction process between the laser-induced surface wave and the defects were simulated. Through the numerical simulation and theoretical analysis, the results show that the amplitude of the reflected wave increases with the depth of the defect and reaches steady state when the depth of the defect is up to a certain value. Instead, the width of the defect has a limited effect on the reflected wave. All of these conclusions can promote the development of the laser-generated ultrasonic technology for the detection and identification of the material defects.