Using the finite element sound field computing software COMSOL,the simulation experiments are conducted on the scattering sound field when Lamb wave is reflected and conducts modal conversion at the right angle plate end of the underwater elastic plate. Through the analysis of the scattering sound field and in combination with the law of energy conservation,the modal conversion efficiency of Lamb wave at the right angle plate end of the underwater elastic plate is calculated by ignoring the clutter wave(such as angular wave),and compared with the theoretical value.