Abstract: Ethanolamine (ETA) as a alkalizer shows a good anticorrosion ability on reducing the corrosion of the secondary circuit system of nuclear power plant. Based on this, in order to enhance the corrosion inhibition effect of ETA and further reduce the migration of corrosion products to steam generator, the corrosion inhibition capabilities of 3 mg/L ETA and different concentrations (0.1, 0.3, 0.5, 0.8 mg/L) of 3methoxypropylamine (MPA) mixed amines water conditions for 304L stainless steel were studied. The secondary circuit conditions were simulated by high temperature hanging plate in autoclave. The corrosion inhibition mechanism was investigated by the combination characterization of differential capacitance curve and AFM force curve test, and the morphology of the corrosion inhibition was also studied. The differential capacitance curve shows that the corrosion of the 304L stainless steel surface was slow down through the ETA+MPA mixed amines water condition. The organic amine molecules in the solution were adsorbed on the metal surface, which changes the electric double layer structure of the metal surface and positive shifts the zeropoint charge potential of the metal electrode. The fitting result of adsorption data conforms to the FloryHuggins isotherm model. The AFM force curve results show that organic amines adsorbed on the surface of 304L stainless steel, which agrees with the change of the differential capacitance of the stainless steel surface. The density and uniform of the adsorption layer increases with the increase of concentration of organic amine. Thus the inhibition efficiency increases. The morphology analysis (SEM) and composition analysis (EDS) results of the high temperature coupons are consistent with the abovementioned differential capacitance curve and AFM force curve analysis results.