In this paper, the analysis models were established to simulate the influence of the change of the free end size on the output voltage and frequency of piezoelectric vibrator, and the change relation of shear stress of the combination surface was obtained by using ANSYS software. The research results show that the open circuit voltage and the frequency of the triple layer piezoelectric vibrators have some form of increases along with the decrease of the free end size, but the shear stress of the combination surface has the big increases ( up to 74% ) , which made the destruction by less shear strength of the triple layer piezoelectric vibrators.