Welding is an important processing method for ships, aircraft, automobiles, trains, pressure vessels, lifting equipment, and other large structures and complex structures. The failure of welded structure, especially the fatigue failure, starts from the surface of welded joint, so the optimization of surface quality of welded joint can improve the performance of welded structure and prolong its service life. The research status of ultrasonic impact treatment on the surface quality improvement of welded joint was reviewed. The influence of ultrasonic impact treatment on the surface geometry of welded joint was analyzed, and the effect of ultrasonic impact on the increase of arc transition radius, the decline of stress concentration factor and the reduction of notch effect were pointed out. The effect of ultrasonic impact treatment on surface residual stress was summarized. It was found that ultrasonic impact treatment caused microscopic dislocation motion and proliferation through macroscopic plastic deformation, resulting in beneficial compressive residual stress in the welding joint surface and sub surface. The influence of ultrasonic impact treatment on the surface micro structure of welded joint was described. The effect of ultrasonic impact on the macro texture and grain size was proposed. The advantages of ultrasonic impact on improving the micro hardness of welded joint and eliminating the surface defects were put forward, and the reasonable ultrasonic impact parameters were pointed out to reduce the surface roughness of the welded joint. Finally, the existing problems were analyzed and the future research directions were prospected.