The invention relates to a high-temperature-resistant and heat-conductive nylon composite material and a preparation method thereof. The high-temperature-resistant and heat-conductive nylon composite comprises the following components in parts by weight: 100 parts of PA66, 40-80 parts of high temperature-resistant nylon, 10-50 parts of a nylon elastomer, 10-30 parts of carbon fibers, 20-50 parts of a heat-conductive filler, 0.2-1.5 parts of a reactive flow modifier, 0.3-1.2 parts of an antioxidant and 0.3-2 parts of a lubricating agent. The preparation method comprises the following steps: uniformly pre-mixing the PA66, the high-temperature-resistant nylon, the nylon elastomer, the heat-conductive filler, the reactive flow modifier, the antioxidant and the lubricating agent, adding from a main feeding port of a double-screw extruder, adding the carbon fibers from a glass fiber mouth, controlling the rotating speed to be 800-1200 revolutions / min and the temperature to be 250-285 DEG C and performing extrusion granulation to obtain the high-temperature-resistant and heat-conductive nylon composite material. The material has excellent high temperature resistance and heat conduction and simultaneously has the characteristics of being good in mechanical property and easy to process.