A plug in piezoelectric cantilever beam is proposed.Through the tip mass is converted into equivalent inertia force and inertia moment,the theoretical formula of its inherent frequency is obtained.A series of piezoelectric cantilever beams with the same inherent frequency and different length width ratio are designed.It can be found that the error between theoretical calculation and simulation result is less than 5% by ANSYS modal analysis,which proves this method of solving inherent frequency is feasible. Moreover,as the increase of length width ratio,the output voltage of piezoelectric cantilever beam and the maximum stress of the piezoelectric layer also increase linearly.This is very meaningful to predicting the performance of piezoelectric cantilever beam. Finally,the fatigue life of the piezoelectric cantilever beams can be calculated by nCode DesignLife, and based on which the optimal design scheme is gotten.A new and relatively complete method of the structure optimization design of piezoelectric cantilever beam can be established.