Abstract : Taking the variable frequency constant pressure water supply system as an example, this paper describes the system composition, function and application of KingSCADA in the system. Keywords : variable frequency drive, KingSCADA, PLC, control instrument 1 Introduction In recent years, with the development of microelectronics technology and computer technology, variable frequency drives, as a kind of intelligent speed control unit, are widely used in various industries such as papermaking, textile, power plant, chemical industry and petroleum due to their versatility, high reliability and obvious power saving effect; programmable controllers not only replace hard-wired logic with logic programming, but also add the function of data transmission and processing, and have unique advantages in terms of small size, complete functions, low price and high reliability; industrial configuration software displays the operating status of monitoring equipment in the form of animation, which is convenient to form a monitoring screen and realize control function; intelligent A/D conversion module has become the bridge for data conversion between the field and the host computer. So we investigated the water supply pump house of a certain hydropower section and the results are as follows: (1) The pump house has 4 water intake wells, and the power of the submersible pumps is 18.5kW. They are responsible for the water supply of residents, stations and trains. When water usage is high, four submersible pumps need to operate at full capacity, while when water usage is low, only one submersible pump needs to operate. Therefore, the number of submersible pumps in operation is greatly affected by the total water supply, and the on-duty personnel frequently start and stop the pumps, resulting in significant potential for energy saving. (2) Data such as power supply voltage, current, single pump flow rate, single pump running time, total pipeline pressure, total flow rate, well water level, and disinfection during water supply need to be manually observed, measured, and then recorded in a form and reported to superiors. (3) The original equipment is relatively outdated, and in order to reduce manpower, reduce consumption, and increase efficiency, it is urgently needed to be upgraded. [b][align=center]For details, please click: Design and Application of Variable Frequency Monitoring System for Pump Room[/align][/b]