Abstract: After using ETA as the p H adjustment agent in secondary Circuit of Qinshan 320 MWe PWR plant in place of ammonia, the p H of Moisture Separator Reheater（MSR） drainage and Stream Generator（SG）blowdown water are obviously increased, so that the corrosion conditions are improved, such as: the corrosion products of the equipment in the water phase decreased, flow accelerate corrosion is restrained and the transfer of corrosion products to the secondary side of the SG is reduced. As more period water output are produced from condensate mixed bed because of ETA applied in the secondary system, the regeneration times and acid, alkali and water consumption when regenerating resins are reduced, so the workload of operation workers can be alleviated and the environment pollution from the waste water are reduced either.