The invention discloses a method for preparing marine zinc chromate antirust paint. The method includes a production step a. The marine zinc chromate antirust paint comprises, by weight, 22-24 parts of cyanamide resin, 25-27 parts of polyester resin, 7.5-9.5 parts of zinc chrome yellow, 1.5-2.5 parts of ethylene glycol, 4-6 parts of tetraethoxysilane, 3.2-6.5 parts of silane coupling agents, 8-10 parts of barium sulfate, 0.5-0.8 part of nanometer-sized phosphoric acid, 5-7 parts of dispersing agents and 0.8-1.2 parts of plasticizers. The method has the advantages that the method is low in raw material cost and harmful chemical consumption, the marine zinc chromate antirust paint is free of optional harmful substances, and anticorrosion, antifouling and antibacterial effects can be realized by the marine zinc chromate antirust paint.