Through the pressure sensor installed on the outlet pipe network, the outlet pressure signal is changed into 4-20mA standard signal and sent to PID regulator. After the calculation and the given pressure are compared, a comparison parameter is obtained and sent to frequency converter, the inverter controls the speed of the motor, adjusts the water supply of the system so that the pressure of the water supply pipe network is kept at a given pressure. According to the size of water consumption by the PLC control of the number of pumps and frequency converter on the pump speed, to achieve constant pressure water supply. Constant pressure water supply equipment working principle system picture constant pressure water supply equipment working principle system picture when the water supply load changes, the input motor voltage and frequency also changes, thus, the closed-loop control system based on the set pressure is formed. In addition, the system also has a variety of protection functions, fully ensure the timely maintenance of the pump and the system's normal water supply.