The invention belongs to the field of tire manufacturing technology, and specifically relates to a sidewall rubber of an automobile tire. The sidewall rubber of the automobile tire is characterized in that the sidewall rubber comprising the following components of natural rubber, butadiene rubber, styrene butadiene rubber, ethylene propylene diene monomer rubber, polybutadiene rubber, zinc carbonate, light calcium carbonate, stearic acid, talcum powder, titanium dioxide, low structure high-abrasion furnace black, white clay, zinc oxide, stearic acid, Santo white crystal, high aromatic hydrocarbon oil, an accelerant, paraffin, Santo flacks, insoluble sulfur, carbon black, aluminium hydroxide, alkyl phenol disulfide and magnesium oxide. By adopting the formula composed by the above components, the sidewall rubber of the automobile tire has relatively good strength and elongation property, can endure atmospheric aging, flex cracks and mechanical damages, can protect the tire body from corrosion of the mechanical damages, sunlight, wind and rains.