A rapid prototyping system for arc welding based on robot is designed and developed, which can realize path planning and automatic rapid prototyping of arc welding. The core of the system is the integrated real-time control platform, which integrates the path planning algorithm and the robot motion control algorithm, and has a good human-computer interaction interface. It can easily carry out basic parts repairing and three-dimensional rapid prototyping research. It also provides free prototyping for arc welding. The research of control method laid the groundwork.