Abstract: In view of problem that terminal water consumption of water supply system in a mining area cannot be determined, a design scheme of automatic constant-pressure water supply system was put forward. The system uses PLC and frequency converter to control water pump to ensure that the pump power and quantity can be automatically adjusted when terminal loads change greatly, so as to achieve constant pressure water supply. The practical application result shows that the system not only ensures the water pressure required by equipment cooling water system and dustproof water system, but also avoids sharp fluctuation of water pressure and reduces failure rate of equipments on working face.