The electromechanical behavior of piezoelectric transformers (PTs) is predicted using a polynomial approach. It is the first time that a polynomial method is applied to study structures made up of both an actuator and a transducer. The method consists in incorporating directly into the equations of motion the continuity and boundary conditions by the use of the delta function. The numerical results are presented such as resonance and anti-resonance frequencies, electrical input admittance and voltage gain of the PTs. The validity of the model is confirmed through a comparison between the results using the polynomial approach and an analytical method. A good agreement was obtained between the results of the proposed polynomial approach and the results using an analytical approach for both the free vibration and forced vibration analysis. The mechanical displacement, the load dependence and the dimension effect are presented to illustrate our model.