Abstract: A method of simplifying finite element model is proposed, which uses the fundamental physical theory of FEM(Finite Element Method) to simplify and analyze the fluid model in some engineering applications without the necessity of calculating precise acoustic parameters and beam characters of radiation sound field.By the ultrasonic transducer simulation with the method, a sample is developed and measured, and the result is substantially in accord with that of the simplified finite element model.Thereby it is proved to be feasible and effective for optimizing trans-ducer design.