The invention discloses a gas-permeable membrane preparation method which includes the steps: (1) mixing and stirring polyethylene resins, chlorinated polyethylene resins, nano-silver, dispersing agents, inorganic fillers and coupling agents to obtain first mixed materials, preparing first base membranes from the first mixed materials, and longitudinally stretching the first base membranes to obtain first gas-permeable membranes; (2) mixing polyurethane, polyhydroxy butyrate valerate copolyester, zeolite, antioxidants, nano-silicon carbide, silane coupling agents, dispersing agents and inorganic fillers to obtain second mixed materials, preparing second base membranes from the second mixed materials, and longitudinally stretching the second base membranes to obtain second gas-permeable membranes; (3) mixing polystyrene resins, polyvinyl chloride resins, polyphenylene sulfide, dispersing agents, inorganic fillers and coupling agents to obtain third mixed materials, preparing third basemembranes from the third mixed materials, and longitudinally stretching the third base membranes to obtain third gas-permeable membranes; (4) sequentially bonding the first gas-permeable membranes, the second gas-permeable membranes and the third gas-permeable membranes from top to bottom, and performing bidirectional stretching to obtain gas-permeable membranes.