Abstract: When multiple AC welding power sources weld a same weldment at the same time, the current of the welding power sources output in series due to the phase out-of-sync and the impedance of the circuit increases, which further leads to the occurrence of overvoltage when the secondary IGBT is turned off. To solve this problem, a coordinated controller that can set the AC phase and frequency is proposed. The controller can realize the synchronous control of the phase, so as to solve the problem of high back-voltage of the secondary IGBT and mutual series of current caused by the asynchronous phase. The coordination controller can realize the setting of the coordination parameters AC frequency and cleaning width, and transmit the parameters to the welding power source through 485 communication, it can also realize the coordination of the phase output of the welding power source to ensure the phase output of the welding power source is consistent. The coordinated controller can realize the setting of AC frequency and duty cycle and transmit the parameters to the welding power source through 485 communication, it can also realize the coordinated phase output to the welding power source to ensure the same phase output of the welding power source.