NOVELTY - The method involves forming macromolecular binder and solvent at a side of material i.e. polyolefin-group single layer, that is formed with coating composition for manufacturing a coated separation film (10) by utilizing nano vapor. The nano vapor is dried with a porous separating film. The coating composition is provided with inorganic particle. The nano vapor is emitted from a drying process based on whole blast air, where thickness of the polyolefin-group single layer is in 4-25 micro meter and a solvent residual amount of the porous separating film is in 80ppm.    USE - Method for manufacturing a porous separating film of a high power and capacity secondary battery (claimed) that is utilized in an electric vehicle.    ADVANTAGE - The method enables preventing thermal shrinkage of the separation film due to high-temperature drying and thermal transformation through introduction of the nano vapor so as to facilitate cold drying and avoid limit of the solvent selection when the high-boiling solvent and moisture is effectively removed, minimize side reaction progressing of a battery by the solvent and moisture, and manufacture the separation film.    DETAILED DESCRIPTION - The macromolecular binder is selected from polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene, polyvinylidene fluoride - trichloroethylene, polyvinylidene fluoride - chloro trifluoro ethylene, polymethyl methacrylate, poly acrylonitrile, polyvinyl pyrrolidone, polyvinylacetate, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinylalcohol, cyanoethylcellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile stirene butadiene copolymer, polyimide and stirene butadiene rubber. INDEPENDENT CLAIMS are also included for the following:    (1) a porous separating film for secondary battery    (2) a secondary battery.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of a secondary battery.'(Drawing includes non-English language text)'    Nano steam generator (3)    Dry air provider (4)    Dry zones (5, 7)    Punching plate (6)    Coated separation film (10)