90%。Welding with trailing peening (WWTP) currently has a problem that the peening force and the peening frequency can not be accurately adjusted for effectively controlling the welding stress and distortion. In order to solve this problem, a new WWTP system was developed based on the electromagnetism control technique. This system applied the technology of constant frequency pulse width modulation (PWM) to design the control circuit. The peening force was adjusted between 0 and 1 000 N, and the peening frequency ranged from 0 to 25 Hz. The experimental results showed that the transverse and longitudinal residual stresses were decreased by 90% on average respectively when the peening force was 700 N and the peening frequency was 2 Hz, compared with the traditional welding system without trailing peening. 