Abstract: A real-time arc welding robot visual control system based on local network with multi-level hierarchy is presented,which consists of intelligence and human-machine interface (HMI) level,motion planning level,motion control level and servo control level.The last three levels form local real-time open robot controller (LRTORC).The master computer as the first level is for visual measurement,movement command generator,welding torch controller and HMI.LRTORC realizes motion planning and motion control of the robot.The system has the function of automated recognition and tracking weld.The principle of the visual control system and LRTORC developed by us is discussed.The swing welding experiment for V-type welding groove is done and the results show that the system has high resolution of tracing weld in real time,works stably and efficiently.The shape of weld mark is good.