In order to detect the inclined microcracks on the surface of the workpiece, this paper analyzes the interaction between the broadband Rayleigh wave generated by the laser and the inclined angle defect on the rectangular aluminum plate theoretically and experimentally. The angle of the defect is measured quantitatively by the transmitted wave, reflected wave and the diffraction wave generated at the crack tip by the Rayleigh wave interacting with the inclined defect. By observing the stress nephogram of the finite element simulation, it is found that Rayleigh waves propagate along the defect, and modal conversion occurs at the tip of the defect. Some waves are diffracted along the crack to the metal surface, and some of the waves are reflected while some are converted into longitudinal and transverse waves. In this paper, through the Fourier transform of the diffracted wave, the frequency spectrum of the diffracted wave is obtained, the trend of the diffracted wave in the frequency domain is observed, and the energy of the diffracted wave is calculated. The energy of the diffracted wave decreases with the increase of defect angle, and it is e exponential decay distribution. Combining finite element simulation with experiments, the results show that when the surface defect and the surface are inclined at a certain angle, the energy extraction of the diffraction wave may be an effective method to detect the inclination angle of the surface defect.