Cu is widely used due to its excellent electrical and thermal conductivity properties. However, its corrosion resistance in chlorine-containing environments (such as seawater or salt fog) is poor, which limits its long-term application in harsh conditions. To address this challenge, herein block composite of Cu/reduced graphene oxide (Cu/rGO) was fabricated via processes as follows: billets of which were prepared by vacuum hot pressing with mixture of Cu powder and rGO as raw material, and then they were successively subjected to hot-forging and -rolling. Further, the corrosion behavior of Cu/rGO composite and pure Cu in 3.5%NaCl aqueous solution and salt fog was comparatively assessed. Results show that the corrosion rate of Cu/rGO composite in NaCl aqueous solution was 34.8% lower than that of pure Cu, this may be mainly attributed to the physical barrier effect of the lamellar rGO, which effectively delayed the penetration of chloride ions and the charge transfer process. The Cu/rGO had a higher charge transfer resistance and higher electrochemical impedance, indicating that the interface reaction was more difficult to occur and the corrosion product film was compact. In the salt spray testing conditions, the corrosion rate of Cu/rGO was only 0.625 × 10^-5 g·cm^-2·h^-1, which was 66.67% lower than that of pure Cu (1.875 × 10^-5 g·cm^-2·h^-1). The number and size of corrosion pits on the surface of Cu/rGO were small and few, and the decrease in yield strength after corrosion (3 MPa) was significantly lower than that of pure Cu (18 MPa). The findings revealed the mechanism of rGO in enhancing the corrosion resistance of copper-based composites from multiple perspectives, including electrochemical behavior, microscopic morphology, and mechanical properties. Which may provide meaningful reference for the application of composite of Cu/rGO in marine engineering and high-humidity, high-salt environments.