In this study, the vibration distribution along the width direction in the output section of a piezoelectric transformer operating at the thickness shear vibration mode is investigated experimentally and theoretically. It is experimentally found that the vibration of output section has a spatial gradient and attenuates as the distance from the input section increases. A theoretical model is developed to estimate the vibration attenuation in the output section, which provides the guidelines of optimizing the transformer and explains some important phenomena such as the nonuniform temperature distribution in piezoelectric transformers. The larger the load resistance, the larger the vibration gradient is. At the resonant frequency, the vibration gradient decreases with increasing the width of the input or output section, and it changes little with the length and thickness of the transformer when the load resistance matches with the piezoelectric transformer. The vibration gradient increases with increasing the length or decreasing the thickness when the load resistance is constant, in which the load does not match with the transformer.