The invention discloses environment-friendly sealing sponge for an automobile air conditioner and a preparation method thereof, and relates to the technical field of air conditioner sealing sponge. The environment-friendly sealing sponge for the automobile air conditioner is prepared from the following raw materials in parts by weight: 80-95 parts of bio-based EPDM, 10-15 parts of polylactic acid fiber, 30-40 parts of carbon black, 1-2 parts of stearic acid, 1-2 parts of zinc oxide, 30-40 parts of kaolin, 25-35 parts of heavy calcium carbonate, 1-3 parts of cashew nut shell oil, 1-2 parts of a foaming agent AC, 1-2 parts of a foaming agent OBSH, 1-2 parts of an accelerant PZ, 1-2 parts of an accelerant NS, 2-4 parts of PEG4000, 1-2 parts of a silane coupling agent, 2-3 parts of sulphur, 1-2 parts of DCP and 1-2 parts of a stabilizer. The environment-friendly sealing sponge for the automobile air conditioner uses the bio-based EPDM as a raw material, so that dependence on a petroleum resource is reduced and the environment-friendly sealing sponge is environment-friendly and renewable; the added biodegradable polylactic acid fiber can further improve the strength and the elasticity of the material; through a reasonable matching ratio of the components, the prepared material is better in performance, high in tensile strength, low in volume weight and small in permanent deformation, and a requirement on the sealing performance of the automobile air conditioner can be met better.