The invention discloses a preparation method of a heat-conducting foaming vulcanized composite butadiene-acrylonitrile rubber sealing strip. The preparation method comprises the following steps of: soaking molecular sieves in nanotitanium dioxide and nanosilicon dioxide suspension, heating by high temperature for activation, hydrogenating modified butadiene-acrylonitrile latex by using a hydrazinehydrate method, adding a coupling agent and an initiator and the like to react for modification, uniformly mixing the activated molecular sieves with polyvinyl alcohol, carbon fiber and zinc stearate, then mixing with modified butadiene-acrylonitrile latex, flocculating with calcium chloride, and after adding other additives, mixing, foaming and vulcanizing to obtain the heat-conducting foaming vulcanized composite butadiene-acrylonitrile rubber sealing strip. The preparation method disclosed by the invention has the advantages that after the butadiene-acrylonitrile latex is modified, and bymixing, foaming and vulcanizing, the prepared sealing strip generates foam holes with closed hole structures, is oil-resistant, heat-resistant, insulated, flame-retardant and tear-resistant and is high in tensile strength.