To achieve the detection of surface crack defects on aluminum plates, a surface crack defect model is established based on COMSOL and the interaction between laser ultrasound and defects is analyzed. To deal with the problem of weak reflection signals and poor signal-to-noise ratio in the propagation of laser ultrasound inside materials, a signal multiple averaging combined with adjacent three-point difference processing method. Three cracks on the surface of 5 mm thick aluminum plate were detected using a laser ultrasonic visualization inspection system. Using multiple signals averaging can increase the signal to noise ratio (SNR) and enhance the damage echo in the maximum amplitude map. Extracting the peak and peak values of the signals at each scanning point in the target area reconstructs the three-dimensional maximum amplitude map. The ultrasonic signals in the horizontal and vertical directions are processed using an adjacent three-point difference processing method, providing better defect visibility. The results show that there is a significant interaction between surface waves ( R) and surface defects within a depth of 1 mm. The laser ultrasonic visualization inspection technology can quickly detect cracks and defects on the surface of aluminum plates, and can display the position and size of surface cracks in three dimensions. The multiple averaging and adjacent three-point difference processing method used can accurately characterize defects above 0. 5 mm, which will have extremely broad application value in industrial non-destructive testing and evaluation.