Abstract: In order to improve the automation degree of semi-cycle hardfacing of boiler superheater and achieve better results of hardfacing, automatic control system of semi-cycle hardfacing for the boiler evaporator tube was designed to replace the traditional manual repeated operation based on Mitsubishi FX series PLC system. And through the communication with welding machine, as well as coordinated action of 3 axis servo motor, the semi-cycle surfacing effect was finally achieved. The system can be used to set the parameters of the water pipe and welding through the touch screen to satisfy the semi- cycle hardfacing for pines with different diameters. According to the final test in the factory, the system not only realized the automatic control of semi-cycle hardfacing, achieved high precision, greatly improved work efficiency, reduced the labor cost, but also ensured the better welding results compared to the manual hanlfacing. The system can greatly improve the degree of auto.mation, reduce the cost, and ensure better welding effect, and eventually meet the requirements.