Abstract: According to the actual service conditions of marine equipment, the corrosion behavior of 20CrMnTi steel in marine environment was studied by means of electrochemical testing, artificial seawater full immersion test, salt spray/dry/wet alternating cyclic corrosion test, galvanic corrosion test and real sea corrosion test. The results showed that the free corrosion potential, free corrosion current density and pitting corrosion potential of the 20CrMnTi steel in 3.5% NaCl aqueous solution were -0.516 V (vs. SCE), 1.563 × 10^-6 A/cm² and -0.473 V (vs. SCE), respectively. There was no passivation interval in the polarization curve. The corrosion rates of the 20CrMnTi steel in artificial seawater full immersion test and salt spray/dry/wet alternating cyclic corrosion test were 78.66 and 2 830.27 μm/a, respectively. When the 20CrMnTi steel was coupled with 05Cr17Ni4Cu4Nb stainless steel, the corrosion rates of the 20CrMnTi steel in the artificial seawater and Sanya real sea were 286.42 and 310.06 μm/a, respectively, and the corrosion was uniform. The salt spray/dry/wet alternating cyclic corrosion could significantly accelerate the corrosion of the 20CrMnTi steel. The corrosion rate of the 20CrMnTi steel in galvanic corrosion test in laboratory was similar to that in real sea, so the galvanic corrosion test in laboratory could effectively simulate the corrosion law of devices in real marine environment.