The invention provides an oxidized grapheme/carbon black rubber nanocomposite and preparation method thereof, which belongs to the field of rubber nanocomposite technology. The nanocomposite comprises the following basic compositions by mass: 100 parts of diene series rubber matrix, 0.5-5 parts of oxidized grapheme, 30-70 parts of hard carbon black of average particle size 11-30nm, 1-10 parts of plasticizer, 6-10 parts of activator, 0.5-4 parts of anti-aging agent, 1-4 parts of sulfuration promoter and 1-6 parts of insoluble sulphur; oxidized grapheme modifier. The oxidized grapheme powder is dispersed in deionized water for ultrasound, and a natural rubber emulsion is added, and masterbatch after flocculation, washing and drying is mixed uniformly with other additives, after sulfuration, the product is obtained. The oxidized grapheme/carbon black rubber nanocomposite has the advantages of excellent processing performance and obviously reduced dynamic themogenesis, thereby improving the usage life of tyre.