Abstract: A kind of automatic surfacing device for guide vane repair based on Mitsubishi PLC control is designed. The combination of frequency converter and reducer motor is adopted to reduce the output speed to meet the requirement of blade shaft surfacing. Three stepper motors constitute the Qadir coordinate system,which controls welding gun to move flexibly in the welding space to finish welding the guide blade.In order to increase stability and reliability of the control system,sensor technology is used to assist PLC to achieve stable and effective control during surfacing.