Abstract: The conventional four-terminal network design method of piezoelectric ultrasonic transducer (PUT) equates the stacked piezoelectric ceramics (SPCs) to a electrical four-terminal network, ignoring the electromechanical coupling process inside the SPCs and increasing the design errors of the transducer. Aimed to obtain a larger ultrasonic amplitude, this article designed two PUTs of different sizes by the four-terminal network and the six-terminal network, named transducer A and tansducer B, respectively. The natural frequency and output amplitudes of the two PUTs were compared and analyzed by finite element method(FEM), and the experiments further verified the validity of the theory and the simulation analysis. When the excitation woltage is same, the results show that the output amplitude of transducer B (designed by six-terminal network) is 1.5 times larger than the amplitude of transducer A, and appling six-terminal network to the PUT designing can improve the vibration performance of PUT certainly.