Abstract: In order to reduce the human participation in specific welding situation, realize welding automation. With STM32 and OV2640 as the core hardware, a weld width measurement system is designed. The RGB565 format image returned by the camera is received through its own DIGITAL camera DCMI interface. Then the image is processed by graying, binarization and regional marking algorithms, and finally the pixels between the two steel plates are counted in real time. The actual distance between the two plates was calculated. Experimental data show that the measurement error of the system can be controlled within 2%, and high precision weld spacing measurement can be achieved, which provides necessary data for the subsequent realization of welding automation, and is expected to be applied in practical engineering.