Abstract: Automatic water replenishment and constant pressure water supply realized by water towers or storage tanks represent a common water supply mode in factories. In this paper, the water supply scheme and overall planning framework of the constant pressure water supply system with an elevated water tower are first determined according to practical operation requirements. Then, PID parameters are configured based on the water supply process. A one-drive-three power main circuit for the constant pressure water supply system is designed, and PLC control programs are compiled. A variable table covering outlet pipeline pressure, motor operating frequency and liquid level for automatic water replenishment is established, and coordinated monitoring is realized on the touch screen. By adjusting the operating frequency of water pumps and automatically switching pumps in response to variations in outlet water pressure, the water supply system achieves dynamic constant pressure water supply for the cooling water system. This work can provide references for the design and engineering application of similar automatic water supply systems.