The core of the nonlinear laser ultrasonic crack detection technology based on laser excitation/detection lies in the fact that it makes the crack to be periodically opened and closed by using mechanical/laser irradiation to apply a load on the sample/crack. However, many factors such as the complex crack morphology and crack wall roughness affect the results. Aiming at this problem, a black glass plane and a convex surface of a plano-convex lens are used to simulate crack walls, by changing the relative position between the black glass and the lens to simulate the real crack closure process. The pulse point laser source is used as the ultrasonic excitation source to excite the ultrasonic wave on the black glass surface, the ultrasonic wave is detected by the laser vibrometer to quantitatively promote the closure process of the black glass simulated crack, and the peak-to-peak value of each modal signal under different push distances is recorded. The experimental results show that the black glass is pushed in a state where the black glass and the convex lens are not in contact at all. With the increase of the black glass push distance, the pressing force between the black glass and the plano-convex lens increases, and the peak-to-peak values of the direct longitudinal wave signal and transverse wave signal have a tendency to become larger. When the pressing force between the black glass and the plano-convex lens is small, the peak-to-peak value of the mode-transition signal of the longitudinal wave to the transverse wave first increases and then decreases, and the peak-to-peak value of the reflected longitudinal wave signal decreases.