Abstract: Using macroscopical inspection,metallographical analysis,fractography analysis and SEM energy spectrum analysis,overall analysis of corrosions in nuclear primary coolant circuit 18-8 stainless steel pipe was performed.The results show that pitting corrosion occurre at the unbent pipe segment,sorme stress corrosion cracking occurre in bend pipe and welding line,and some intergranular corrosion occurre also at welding line.Above corrosions resulted from the properties of the pipe material and chloride ion assembling due to seawater dripping down on pipe surface.