Abstract: The energy relationships among all the elements,by which the magnetostrictive transducers are manufactured are analyzed by using finite element method (FEM) for the first time,then the expressions of FEM dynamics equations and performence formulas for magnetostrictive transducers are derived.The vibrating modes of the class Ⅶ transducer and its shell are calculated theoretically and the results show that ther is a breathing mode and if the transducer works at this mode,the transducer will vibrate with a greater volume speed and source level.