The invention provides a butadiene-acrylonitrile rubber/attapulgite/carbon black nanocomposite and a preparation method thereof. The preparation method comprises the following steps: step 1, weighing, by weight, 1 to 40 parts of attapulgite, 1 to 60 parts of carbon black, 1 to 20 parts of a plasticizer, 1 to 10 parts of an activator, 1 to 5 parts of a vulcanization accelerator, 1 to 6 parts of sulfur and 0.1 to 5 parts of an antioxidant; step 2, dispersing attapulgite and carbon black in water to prepare attapulgite/carbon black suspension, then adding butadiene-acrylonitrile rubber which accounts for 100 parts by weight in terms of a dry basis, maintaining a temperature to be 30 to 60 DEG C, carrying out stirring, adding a flocculating agent for flocculation and carrying out dehydration and drying so as to obtain butadiene-acrylonitrile rubber/attapulgite/carbon black masterbatch; and step 3, uniformly mixing the masterbatch obtained in the step 2 with the plasticizer, the activator, the vulcanization accelerator, sulfur and the antioxidant weighed in the step 1 and carrying out vulcanization so as to prepare the butadiene-acrylonitrile rubber/attapulgite/carbon black nanocomposite. The method enables attapulgite to be uniformly dispersed in a rubber matrix and to exert cooperative strengthening effect together with carbon black; and the prepared nanocomposite has excellent mechanical properties and processing performance.