In this article, the technology of ultrasound impacting is mentioned. The toe of 16Mn welded joints are treated by the ultrasound impacting, and the fatigue, hardness and residual compressive stress of the 16Mn welded joints are compared after treated by ultrasound impacting. The results shows that, the ultrasound impacting bring high residual compressive stress on the surface of the 16Mn welded joints, besides, the treatment of ultrasound impacting can improve the fatigue and hardness of the 16Mn welded joints, and when the impacting electric current is 1.5A, and the impacting time is 10 min, the fatigue and hardness of the sample is the best.