Belonging to the field of functional polymer materials, the invention in particular relates to a thermal conductive MC nylon composite material and a preparation method thereof. By means of the principle of in situ polymerization reaction, graphite, a caprolactam monomer and the like are subjected to in situ polymerization reaction to obtain the thermal conductive MC nylon composite material. Because of the in situ polymerization reaction, graphite is uniformly dispersed in an MC nylon matrix, and the interface interaction force between the graphite and MC nylon matrix is strong, thus being conductive to conduction of heat at the interface, reduction of interface thermal resistance, and utilization of stress transfer at the interface. Therefore, the prepared thermal conductive MC nylon composite material has obviously improved thermal conductive performance, and the strong interface effect also enhances the mechanical properties and thermal stability of the thermal conductive MC nylon composite material. The thermal conductive MC nylon composite material prepared by the invention can meet the demands of thermal energy utilization, chemical heat exchange and other fields for high performance thermal conductive composite materials.