Abstract: Lamb wave plays a significant role in plate defect testing, but the visualized research on Lamb wave scattering at cracks is still not enough. In this paper, the laser-ultrasonic visualization inspection method is used to inspect the reflection and transmission of the laser excited broadband Lamb wave at a crack of 0.4 mm deep and 0.2 mm wide. In addition, the scattering characteristics of Lamb wave with different center frequencies at cracks are studied by band-pass filtering technique. It is found that the mode transformation of Lamb wave occurs at cracks and a mode with faster velocity is found. As the frequency increases, the reflected Lamb wave is getting more energy. This research offers an experimental reference for the crack detection of Lamb wave.