In order to detect the insulation defects of high voltage switchgear timely and ensure the safe operation of power grid, a portable detection device for partial discharge in switchgear is developed based on TEV and ultrasonic wave methods in this paper. The built-in TEV sensor and ultrasonic wave sensor are both used for combined detection, which not only improves the accuracy of detection, but also improves the efficiency of detection for maintenance personnel owing to its small size and simple operation. This paper describes the overall system structure and hardware implementation of the device in detail, and a partial discharge detection platform for switchgear was built in the laboratory after successful development to verify the effectiveness of this device. Furthermore, this device was compared with the product of EA Technology. The results show that this device has high detection accuracy and good industrial application prospect.