The article researched on edge extraction system of the laser welding image based on ARM micro controller. The system can achieve accurate extraction on the edge of the laser welding pool, and reduce the system cost effectively while satisfying the real-time constraints. With STM32f103 controller for the system as the core, the outside are image storage and display module. The image processing methods of gray-scale transformation, image smoothing, threshold segmentation and edge extraction are realized in ARM, and the processed images are displayed in LCD. The experimental results show that the system researched in this paper can extract color molten pool image edge accurately without distortion and better reflect the relationship between welding parameters and weld pool geometry size, and provide the basis for building real-time control system of the laser welding quality.