Abstract: In order to solve the problem that the content of SO42-in Steam Generator significantly increased beyond the criteria after the use of the condensate treatment （ATE） system in Daya Bay Nuclear Power Plant and Ling’ao Nuclear Power Plant PhaseⅠ, technical improvement have been conducted on the sizes of the fore cation bed and the mixed bed, water distributing devices,ion exchange resins and separation facility. The effectiveness for the ion exchange of the mixed bed is improved, the resolved substance of cation resin is decreased; it is more impossible for fragments and powder which would lead high SO42-content in Steam Generator. Finally,the quality of the steam-water could be improved and ensured.