The invention discloses an explosion valve tension bolt weakening groove surface ultrasonic impact treatment device and a working method thereof, and belongs to an axis part circumferential groove surface strengthening device and method. According to the explosion valve tension bolt weakening groove surface ultrasonic impact treatment device and the working method thereof, the ultrasonic impact amplitude is adjusted to be 20-30 [mu]m, a tension bolt is driven to rotate by a rotating driving mechanism, and thus the rotating linear velocity of the hyperboloid of an impacted weakening groove is 0.8-1.2 mm/s; and a power supply is turned on, the tension bolt weakening groove is subjected to impact treatment, and the suitable impact strength is 10-15 s/mm by the impact time per unit length. A lot of practice proves that the treated tension bolt weakening groove is smooth and clean in surface and remains unchanged in shape; the surface hardness and residual stress of the bottom surface of the weakening groove in the circumferential direction of the tension bolt are uniform and consistent, so that uniform and consistent surface strengthening of the surface of the weakening groove is achieved; fully-automated operation is achieved, the efficiency is high, and technological repeatability is good; a plastic deformation layer with the thickness greater than 1 mm and difficult to achieve through other strengthening method can be obtained; the clean and environmental protection effects in the processing process are achieved, and workpieces are not polluted; and the technology is simple,parameters are less, and monitoring and adjusting are easy.