Abstract: The finite element model of piezoelectric composites on coupling vibration of piezoelectric compound transducer is established,by using commercial finite element method,the effect of piezoelectric composites on the vibration mode and the resonant frequency of piezoelectric compound transducer has been investigated,the relationship between resonant frequency and the geometric dimensions of piezoelectric composites is also analyzed. The results show that the vibration modes will be changed with the different piezoelectric composites,and the first two resonant frequency difference will be changed due to the base material of piezoelectric composites of different young’s modulus and poisson’s ratio,namely resonant frequency difference will be increased with the increasement of base material young’s modulus,but will be decreased with the increasement of poisson’s ratio; the resonant frequency of the transducer is decided by the geometric dimensions of piezoelectric composites,the first two resonant frequencies will be reduced with the increasement of the geometric dimensions of piezoelectric composites,but the space of the two frequencies will be larger.