Abstract: Circulating water pumps feature a relatively large amount of power consumption due to its large power capacity. The transformation of circulating water pump of Unit 2 in a plant is described, and analyses are performed on the income and operation control upon transformation. After the frequency conversion transformation in the main-engine circulating water pump, the operation frequency of the main-engine circulating water pump enables automatic control, which reduces the operation volume of the operator on duty, reduce the risks of human misoperation, and make adjustments more precise. The frequency conversion transformation of circulating water pumps significantly improves the economic benefits, safety and reliability of the plant.