Abstract: The paper summarizes the shutdown wet protection condition of the steam generator (SG) in Qin Shan nuclear power plant. It is measured in laboratory that the corrosion rate and the sludge production rate of the SG shell(S271) and the feed-water pipes (A3) under the shutdown wet protection condition. The effect of air on the corrosion rate and the sludge production rate of S271 and A3, and the inhibition of hydrazine are also studied.