Abstract: To comprehend the corrosion behavior of 18Cr2Ni4WA steel in marine environments and to guide its protection during service, a series of experiments were conducted, including full immersion test in artificial seawater, electrochemical tests, salt spray/dry/wet cyclic tests, galvanic corrosion tests, and real sea corrosion tests. The results reveal that the corrosion rate of 18Cr2Ni4WA steel after 1, 000 hours of full immersion in artificial seawater was 74.64 μm·a^-1. In a 3.5% NaCl solution, the pitting potential was -0.371 V, the corrosion potential was -0.407 V, and the corrosion current density was 1.207×10^-6 A·cm^-2. Under salt spray/dry/wet cyclic conditions, the corrosion rate after 1 000 h was 1 763.28 μm·a^-1. When coupled with ZCuA110Fe3 steel, the corrosion rate in artificial seawater was 237.42 μm·a^-1 with a galvanic corrosion coefficient of 2.14 at an anode-to-cathode area ratio of 1∶1, and 528.33 μm·a^-1 with a galvanic corrosion coefficient of 4.77 at an anode-to-cathode area ratio of 5∶1. In a two-year real sea environment test in the tidal zone of Sanya, the corrosion rate of 18Cr2Ni4WA steel in the couple was 155.07 μm·a^-1. The laboratory galvanic corrosion test results were similar to those of the real sea couple corrosion tests, demonstrating that the simulation device could accurately reflect the corrosion patterns in the real sea environment. The salt spray/dry/wet cyclic test could be used for accelerated evaluation of the material's corrosion behavior in actual marine environments.