Abstract: Provided are a coating for preventing marine biofouling and a preparation method thereof, wherein, the coating for preventing marine biofouling, including an antifouling cladding layer disposed on a metal substrate, the antifouling cladding layer is a metastable-phase antifouling cladding layer; the antifouling cladding layer includes a dispersedly distributed Fe-rich precipitation phase and a Cu-rich solid solution containing supersaturated Fe, and the Cu-rich solid solution containing supersaturated Fe is a Cu—Fe—Sn—Si—P copper-based solid solution; the antifouling cladding layer is prepared by a raw material of a Cu—Fe—Sn—Si—P alloy powder; the Cu—Fe—Sn—Si—P alloy powder is prepared by the following raw materials in mass percentage: Fe: 8% to 40%; Sn: 0.3% to 8%; Si: 0.1% to 0.5%; P: 0.1% to 0.5%; and Cu as a balance; and the metal substrate is selected from the group consisting of a steel substrate, a copper alloy substrate, a titanium alloy substrate, and an aluminum alloy substrate.