Abstract: The load of fan and water pump accounts for more than half of industrial power consumption in China. The power consumption of fan and water pump is in direct proportion with cubic of the practical load. Therefore,applying variable speed motor and suitable pump station units may save electrical energy,and then produce tremendous economic benefit. This paper discusses the mechanical performance of pump,develops the operating scheme of energy-saving of pump units and computation method of optimum pump speed,and presents the closed-loop control chart.