The invention relates to the field of power plant circulating water pumps, in particular to a maintenance method for a flange of a water pump body. The repair method for a corroded flange ring on a water outlet pipe of a circulating water pump body includes the steps that the flange ring to be repaired is divided into at least two repair zones, at least two flange bolt installation holes in continuous positions are contained in each repair zone, and each repair zone is provided with a pressing plate; then, the repair zones are polished respectively and are underlaid with the pressing plates after being polished to be flat, flange bolts are screwed again, and the repair work is completed. According to the method, the flange ring is divided into the flat zones, at least two adjacent flange bolt installation holes are contained in each zone, and each flatted zone is underlaid with one pressing plate, so that the problem of bolt looseness caused by corrosion is solved, and the requirement for the flatting process is lowered; after the water pump is repaired, it is avoided that due to breakdown or damage of the circulating water pump, a turbogenerator unit operates in a load-down mode, and it is ensured that the turbogenerator unit operates safely and stably.