Abstract: In view of requirements of underground separation and backfilling and utilization for coal and gangue, the paper proposed a design scheme of photometric separation system for coal and gangue based on laser 3D scanning and dynamic weighing. Firstly, the system uses weighing unit to weigh measured object, and extracts laser line from each image of the measured object to calculate areas of optical section of the measured object. Then the system uses recognition algorithm to recognize coal and gangue according to volume and weight of the measured object, and sends separation signal to driving unit of separation for coal and gangue according to recognition result, so as to realize real-time online separation for coal and gangue. Test result shows that the system can recognize coal and gangue accurately combining with relative actuator and its recognition rate is 90%.