The utility model provides a partial discharge detector, detection device contains sensing chip, at least one ultrasonic sensor and at least one focus plane of reflection, the focus plane of reflection is parabolic antenna, be used for through parabolic antenna's concave structures reflected ultrasonic waves, ultrasonic sensor set up in the focus position of focus plane of reflection is used for receiving focus on the ultrasonic wave of plane of reflection reflection and generate ultrasound data, sensing chip with ultrasonic sensor links to each other, is used for the basis ultrasound data obtains partial discharge information. With this, to receive the in -process at ultrasonic signal and adopt the parabolic antenna technique, the partial discharge signal that will disperse had both strengthened the signal focus on ultrasonic sensor again through the reflection on effectively, had suppressed the interference again to realize local discharge signal processing device, had good validity.