Abstract: The corrosion behavior of Q235B steel for seawater pipeline in the third generation nuclear power plant was studied by immersion corrosion testing and electrochemical testing in 3.5% (mass fraction) NaCl solution. The results show that with the increase of temperature, the open circuit potential and electrochemical impedance of the Q235B steel decreased, and the corrosion rate increased, indicating the corrosion resistance of the steel became worse. The increase of temperature not only promoted the dissolution of the steel, but also promoted the formation of corrosion products. At 20 ℃ and 30 ℃, the corrosion products were mainly composed of α-FeOOH and α-Fe₂O₃. At 40 ℃ and 60 ℃, the corrosion products were composed of a large amount of α-FeOOH and a small amount of α-Fe₂O₃ and γ-FeOOH, and the relative content of α-FeOOH increased significantly compared with that at 20 ℃ and 30 ℃.