The invention discloses a polystyrene plastic coating. The polystyrene plastic coating is prepared from polystyrene plastic, a butyl acetate solution, a cyclohexanone solution, a methylbenzene solution, active nano-calcium carbonate, polyoxypropylene glycerol ether, an antioxidant DNP, epoxy resin adhesive, water, a DEHP plasticizer, OP-10 and sodium dodecyl benzene sulfonate. The preparation method of the polystyrene plastic coating comprises the following steps: (a) crushing the polystyrene plastic until the volume of the polystyrene plastic is 0.1 to 0.25cm<3> and then washing and drying; (b) adding the crushed polystyrene plastic into a stirring vessel which holds the butyl acetate solution, the cyclohexanone solution and the methylbenzene solution, heating and stirring; (c) filteringmaterials obtained in the (b), adding the active nano-calcium carbonate, the polyoxypropylene glycerol ether, the antioxidant DNP, the epoxy resin adhesive, the water, the DEHP plasticizer, the OP-10and the sodium dodecyl benzene sulfonate, heating, stirring and then cooling, thus obtaining a finished product. According to the polystyrene plastic coating disclosed by the invention, secondary useand multiple use of the plastics are realized; in addition, the coating has the advantages of excellent waterproof property, toughness, stability, smoothness and adhesion.