Abstract: It is a kind of multimode lamb wave that motivates the Acousto-ultrasonic(AU) signals when a thin plate is tested by the AU method. Lame waves can evaluate the quality of the structure of adhesive joints. The relationship between propagation characteristic of lamb and bonding strength of the joints is the effective application of this technology. In this paper, an FEM method is used to simulate the acousto-ultrasonic in the adhesive joints and combines cohesive strength with the propagation characteristic of lame waves in the frequency from 0.5 MHz to 1 MHz. It shows the variation curves of lame wave mode energy as the cohesive strength is lower. This method provides theoretical basis for the experimental studies and the actual testing.