A new type of the longitudinally polarized sandwich piezoelectric ceramic ultrasonic transformer was proposed. Using the equivalent circuit method the electromechanical characteristics of the piezoelectric vibrator was analyzed. The analytical solutions of the input impedance, the resonance frequency, the anti-resonance frequency, the voltage gain were obtained. The relationships of the resonance frequency, anti-resonance frequency, the electromechanical coupling coefficient, the voltage gain and the longitudinal lengths of the transformer, electric load resistance were obtained. The electromechanical coupling coefficient of first resonance mode has the maximum value in the certain size or electric load resistance. The voltage gain of first resonance mode has the maximum value in the certain size.The ANSYS simulation and the measured value of resonance frequency verified the analytical results. The results show that the simulation results and the experimental results agreed with the calculated results.