The invention relates to an automobile braking air chamber rubber diaphragm sizing material formula taking butadiene-styrene rubber as a main sizing material. The formula comprises the following raw materials in parts by weight: 55-100 parts of styrene-butadiene rubber, 0-30 parts of natural rubber, 0-25 parts of cis-butadiene rubber, 0.3-2.5 parts of a vulcanizing agent, 1.0-3.5 parts of an accelerating agent, 3-5 parts of zinc oxide or a substitute, 1-3 parts of stearic acid, 2-4 parts of an anti-ageing agent, 0.5-1.5 parts of a demolding agent, 0-1 part of a dispersing agent FL, 0-5 parts of an adhesive RC or a substitute, 50-100 parts of carbon black and 0-25 parts of a softening and plasticizing agent. The formula has the beneficial effects that: the styrene-butadiene rubber and a small amount of natural rubber are used together, and a vulcanizing system is adjusted correspondingly, so that the problems of high compressive permanent deformation caused by the adoption of butadiene-styrene rubber as a main body sizing material, over high crack expanding speed of flex cracking, low bonding performance, low tensile strength, insufficient product service life caused by frequent insufficient load pressure on the product, and the like can be solved.