Abstract: The deep-sea corrosion test of Ni-Cr-Mo-V high strength steel in the deep-sea environment of the Western Pacific Ocean was carried out by a deep-sea high-efficiency tandem test device. The corrosion behavior of the steel at 500, 800, 1 200 and 2 000 m sea depths was studied by means of scanning electron microscopy, energy dispersive spectroscopy, Raman spectroscopy and scanning Kelvin probe. The results show that the corrosion rates of Ni-Cr-Mo-V high-strength steel exposed to 500, 800, 1 200 and 2 000 m deep-sea environment for 1 a were 0.130, 0.096, 0.093 and 0.081 mm/a, respectively. The corrosion rate decreased with the increase of depth. In the deep sea environment, shallow dish-like pitting pits were formed on the surface of the steel, and pits in some areas merged to form uniform corrosion morphology. The corrosion products of the steel in deep sea environment mainly included α-Fe₂O₃, γ-FeOOH and α-FeOOH.