Abstract: Based on the actual service conditions of marine equipment, the corrosion behavior of HDR steel in marine environments was studied using methods such as corrosion electrochemical testing, artificial seawater testing, and Sanya real sea corrosion testing. The results show that the self corrosion potential E_corr of HDR steel in 3.5% (mass fraction) NaCl solution was -0.151 6 V, the corrosion current density J_corr was 3.46×10^-7 A·cm^-2, and there was no passivation zone in the polarization curve. The corrosion rate of HDR steel in salt spray/dry/wet alternating cycle test and in artificial seawater was 0.369 0 μm/a and 0.374 2 μm/a respectively, and it decreased from 0.91 μm/a at 3 months to 0.08 μm/a at 24 months in real seawater. The comprehensive evaluation shows that HDR had excellent resistance to seawater corrosion. After 2 a of actual seawater corrosion tests, HDR steel mainly experienced localized corrosion and could be used as a replacement material for the current materials 40Cr and 2Cr13 steel.