The invention discloses a preparation method of an oil-water separation membrane, and belongs to the technical field of environmental protection. According to the method, wood stone fiber is mixedintopolyvinylidene chloride melt in a suitable temperature condition, and lignin reaches glassy state, is softened and flows under high pressure; nanofiber sponge is prepared from resin soaked activatedstone pulp; sea-foam stone powder in the activated stone pulp belongs to a magnesium-enriched silicate compound, can magnesium hydroxide crystal and ammonium phosphate under the action of ammonia gasand phosphoric acid, not only ensures that oil absorption sponge has high porosity, but also ensures that the oil absorption sponge has certain flame retardant property; firstly scale has a bionic hydrophobic structure, and a separation membrane structure with a hydrophobic exterior; finally during the process of copper film plating, the internal surface area of fiber fabric is greatly increased through activation of phosphoric acid, and a plurality of active centers are formed in the surface of the fiber fabric; granule suspension oil and dissolved oil liquid can be easily absorbed into interiors of pores, so that damage to the inner surface of the fiber sponge is weakened when the inner surface is scoured by liquid, and the oil-water separation membrane has a wide application prospect.