Abstract: For the arc welding inverter,the voltage mode was usually adopted,which contained only one control loop.For this mode,the transient response was slow,and it couldn't provide the flux balance of the main transformer and current limited of power devices,which decreased the reliability of the power supply.In this paper,the peak current mode is adopted,which contains two loops.The inner loop controls the peak current,while the outer loop controls the average current.In each period,the peak current of IGBTs is controlled,therefore the flux balance is obtained and the transient response is greatly improved,while the precision of the output current and reliability of system are improved.