Abstract: WAVE 2000 numerical software was used for ultrasonic Lamb wave simulation of the inner wall bubble defect of a 16 mm thick artificial test plate.The results showed that it was feasible to detect the hydrogen bubbles in the inner wall of pressure vessel plate by using Lamb wave from the outer wall, and the optimal detection parameters were given, the reference of important parameters such as Lamb wave mode, frequency, incidence angle for actual testing was provided.According to the simulation results, the optimal detection parameters were used for Lamb wave testing, which was not only able to detect defect, but also had high localization accuracy.