The invention provides sponge foaming rubber for a car door sealing strip and a preparation method thereof, a car door sealing strip and a preparation method thereof. The sponge foaming rubber for the car door sealing strip, provided by the invention, is prepared from the following components in parts by weight: 20 to 40 parts of ethylene-propylene-diene monomer 9090M, 69 to 92 parts of ethylene-propylene-diene monomer V8800, 5 to 7 parts of active zinc oxide, 1 to 2 parts of stearic acid, 1 to 3 parts of a dispersant, 0.8 to 1.4 parts of erucamide, 1 to 2 parts of PEG-4000 (Polyethylene Glycol-4000), 5 to 10 parts of POE (Polyolefin Elastomer), 60 to 77 parts of paraffin oil R-2291, 30 to 50 parts of carbon black N550, 50 to 70 parts of carbon black SP5000, 1.5 to 2.5 parts of sulfur S-80, 6 to 10 parts of a moisture absorbent GR, 3 to 6.4 parts of an accelerant, 3 to 3.6 parts of a foaming agent OBSH-75 (Oxydibenzenesulfonyl Hydrazide-75) and 1.1 to 1.5 parts of a foaming agent AC3000-75. By adopting a formula of the sponge foaming rubber for the car door sealing strip, provided by the invention, the prepared sponge rubber has relatively low density and can meet a lightweight design; meanwhile, the obtained rubber also can have relatively good physical performance, so that the utilization quality of the car door sealing strip utilizing the sponge foaming rubber can also be improved.