Abstract: The energy consumption of the vacuum system of the condenser in gas-fired power plants is a key factor affecting the economic efficiency of the units. This paper takes the 2×460 MW combined cycle units of CNOOC Zhuhai Power Plant as the research object. Aiming at the problems such as excessive design margin of vacuum pumps, high energy consumption and deterioration of high-temperature performance, an energy-saving renovation scheme of parallel a set of "water ring-Roots" high-efficiency vacuum pumps on the original vacuum system is innovatively proposed. A comparison of the renovation data of similar power plants shows that the high-efficiency vacuum pump system can achieve an electricity-saving rate of 90.4%, effectively improving the economic efficiency of the condenser vacuum system and the unit, and realizing energy conservation and consumption reduction.