According to the operating principle of piezoelectric vibrant soundbridge, the paper build the dynamic model which couple the piezoelectric transducer and round window in inner ear, and deduced the electron-mechanical transfer function of the model. Through simulating experiments in Matlab, the parameters influenced the system such as piezoelectric deformation constant, support mass, support stiffness were discussed and optimized. The results assigned the theoretical basis in the development of a new piezoelectric vibrant soundbridge.