Abstract: Equipment of welding with trailing peening uses gas as motivity at present. Its disadvantage is excessive extra equipment, lower control precision. In order to improve its disadvantage and increase production efficiency, the automated control system of welding with trailing peening using MCU(Micro Control Unit) AT89C52, the infrared thermoscope FA2B, the A/D converter MAX191, the stepping motor 85BYG-450B was designed. The AT89C52 single-chip is control system core. The temperature parameter was gathered by infrared thermoscope which tracked the weld, MAX191 transforms the signal from analog to digital, 85BYG-450B stepping motor and 2H090MH stepping motor driver were used as driving device. The main control circuit was made up of temperature acquisition unit, peening parameter control unit and stepper motor control unit. Through the repair experiment on the low-carbon steel attrition specimen, the experimental results show that the control system has a small volume, the circuit is reliable, welding defect is clearly improved for example blowhole, crack and so on.