Abstract: To recover the relationship between the received testing signals received and the inner state of adhesive, finite element method is used to calculate and analyze the process of ultrasonic testing of bonded parts. Excitation signal in ultrasonic testing is quantitatively described, and then it is sampled and applied as a displacement load to the probe area. First, ultrasonic testing of bonds with good adhesion is calculated and the corresponding echo signal received by the probe is determined; then, the testing is analyzed again by using a more narrow pulse; finally, testing of several adhesive bonds with different de-bonding state is evaluated and the received signals are compared. The results show that it is necessary to enhance the resolution of the probe in order to evaluate the quality of thin adhesive layer between steel layer and lead layer. Then, signal related with adhesive bonds can be identified, and this signal can be used to evaluate de-bonding quantitatively.