the general corrosion behavior of 304NG stainless steel in simulated pressurized water reactor(PWR)primary loop was studied using still autoclave,the corrosion test lasted for 1680 hours.The corrosion oxide films were analyzed macroscopically and microscopically.The general corrosion and general corrosion rate of 304NG stainless steel was quantitatively valued.Results showed that the oxide film was formed on the surface of 304NG in 14 days.Oxide films were two sub-layers structure,the diameter of oxide particles near the metal substrate ranged from 50 to 100 nanometers,which is compact layer with abundant chromium+nickel less iron,polygonal bigger oxide particles with diameter ranging from 0.5 to 1.6 microns were distributed on the small particles,which is loose layer with abundant iron less chromium+nickel.After 70 days experiment of high temperature and high pressure,the small particles near the metal substrate grew up to 90 to 130 nanometer diameter,the bigger oxide particles grew up to 0.5-2.5 microns,and the ratio Fe: Cr+Ni declined further.The compact and small particle oxide film was very corrosion resistant.The weight gain rate of samples declined very much firstly,and then changed little.After 1680 hours corrosion test,the general corrosion rate declined to only 1.83×10-4mg/dm2·h.