The invention discloses an automatic dressing device for a diamond grinding wheel, which is mainly composed of a workbench, a chuck, and a cylinder body. The chuck is fixed under the upper top plate of the workbench. The gear (12), the large bevel gear is connected with the slider (15), the transducer (9), the horn (13) and the diamond pen (14) are installed on the slider, and the transducer is connected with the ultrasonic generator , the ball screw is connected to the servo motor through the static support plate, the guide shaft is connected to the upper cylinder and the static support plate through the dynamic support plate, the three-phase asynchronous motor is connected to the grinding wheel (23) through the main shaft, and one end of the circuit board is connected to the The proximity switch is connected, and the other end is connected with the servo motor and the three-phase asynchronous motor respectively. The invention can realize the ultrasonic elliptical vibration of the diamond pen, improve the processing efficiency and precision of the grinding wheel, enhance the rigidity and stability of the cutting system, prolong the service life of the diamond pen, and is more suitable for dressing of the hard grinding wheel.