The circulating water pump is one of the main energy consumer equipment in thermal power plants. Hence

it has large energy-saving space. This study establishes calculation models of constant speed pumps

variable frequency pumps and the combination of various pumps. Example calculations are executed under both the discrete and continuous flow conditions for two constant speed pumps

the combination of one constant speed pump and one variable frequency pump

two variable frequency pumps and other different combinations. And then the power consumptions of pumps under different modification schemes are obtained. The results show that

the combination of two variable frequency pumps can work in the best status under various working conditions. Under the conditions of being able to be realized by the two-speed pumps

when the flow rate is 18.68 m3/s

two variable frequency pumps can save energy over 182.6 k W than the combination of two two-speed pumps. When the flow rate is 15.58 m3/s

the combination of two variable frequency pumps can save energy over 778.5 k W than the combination of one variable frequency pump and one constant speed pump. The calculation and analysis can provide a guidance for technical reconstruction of circulating water pump and energy-saving optimization of thermal power plant.