In partial discharge detection of transformer, supersonics detection method is applied widely. In the paper, a model of supersonics is established by MATLAB. Meanwhile, analyses about the relation between amplitude of sound pressure and discharge capacity and ultrasonic signal spectrum are implemented based on the model. By analyzing the partial discharge characteristics of ultrasonic signals, a suitable ultrasonic receiving sensor can be selected that meets the performance requirements. Therefore, detection band of sensor is determined. Meanwhile, the structure of the sensor and the selection of piezoelectric crystals are introduced in details.Finally,the design of ultrasonic receiving sensor is determined.