The invention relates to air-permeable microporous film masterbatch and further relates to a masterbatch containing plastic film and a preparation method thereof. The water-foamed, antibacterial and air-permeable microporous film masterbatch contains a polyolefin polymer, a modifier, a microporous water-absorbing inorganic expanded material, an initiator, a surfactant and a plastic antioxidant. The water-foamed, antibacterial and air-permeable microporous film contains the water-foamed, antibacterial and air-permeable microporous film masterbatch and blow-molded film plastics. The preparation method comprises the steps of granulating the masterbatch, then, carrying out water absorbing aging, adding the blow-molded film plastics, carrying out mixing, and adding the mixture into a foaming and extruding film blowing machine for extrusion, thereby preparing the film. The water-foamed, antibacterial and air-permeable microporous film provided by the invention has the characteristics of simple and stable preparation process, good processability and the like; a water foamer is adopted, is environment-friendly and safe and has an antibacterial function, and the extruded antibacterial and air-permeable film is controllable in micropore density, has the characteristics of fine and uniform open porous texture and cell size, and the like and has the characteristics of excellent comprehensive mechanical properties, environment-friendliness, easiness in recovery, and the like.