In this study, multilayer piezoelectric transformer was manufactured using the PMN-PNN-PZT ceramic and then the electrical characteristics were investigated according to the variations of frequency and load resistance. The voltage step-up ratio of multilayer piezoelectric transformer showed the maximum value at the vicinity of 75 kHz and increased according to the increase of load resistance. When the output impedance coincided with the load resistance, the multilayer piezoelectric transformer showed the temperature rise of less than $20^{circ}C$ at the output power of 20 W. As the results, the multilayer piezoelectric transformer manufactured at low co-firing temperature of $940^{circ}C$ using PMN-PNN-PZT ceramics could be stably driven as the step-down transformers.