Abstract: The present application relates to a steel for grade R6 offshore mooring chain for use in anchoring and mooring floating bodies with cathodic protection: the chemical composition are C 0.18˜0.24%, N 0.006˜0.024, P 0.005˜0.025, S?0.005, Si 0.15˜0.35, Mn 0.20˜0.40, Cr 1.40˜2.60, Ni 0.80˜3.20, Mo 0.35˜0.75, Cu?0.50, Al?0.02, Ti?0.005, V 0.04˜0.12, Nb 0.02˜0.05, Ca 0.0005˜0.004, O?0.0015, H?0.00015, the balance is Fe: the total content of alloy ?M=(Si+Mn+Cr+Ni+Mo+Cu), 3.4<?M?6.8; the total content of microalloy ?MM=(Ti+Al+Nb+V), 0.065??MM?0.194. The corrosion potential is adjusted to prevent hydrogen embrittlement caused by cathodic overprotection on the basic premise of maintaining the strength, toughness and low corrosion rate of the steel.