Ethanolamine (ETA) is a kind of pH control agent in all volatile treatment (AVT) in nuclear power plant. In this article the corrosion behavior of carbon steel and nickel based alloy 690 in solutions with different ETA concentration was investigated. Corrosion morphology of both metal was observed using scanning electron microscope (SEM) and composition of their oxide is analyzed by X-ray photoelectron spectroscopy analysis (XPS) and X-ray diffraction (XRD). It was discovered that the oxide formed on carbon steel was Fe₃O₄ and its pitting became fewer and shallower as ETA concentration increased, which suggested strong inhibiting effects of ETA on carbon steel pitting; while the duplex structure was not discovered in oxide formed on alloy 690, only peak of Cr was found in the oxide on alloy 690 immersed in 40, 50, 80 mg/L ETA solutions. Electrochemical experiments results under 280 ℃ showed in 20 mg/L and 40 mg/L ETA solution the electrochemical behavior was nearly the same, relevant parameter of linear polarization was of small difference, while the corrosion current of carbon steel dropped to 1/9 and corrosion current of alloy 690 dropped to 1/3 and the polarization resistance increased significantly in 80 mg/L ETA solution compared with those in 20 mg/L and 40 mg/L ETA solution.