The invention belongs to the field of polymer matrix composite manufacturing, and particularly relates to a preparation method of a carbon nanotube-graphene oxide mixed reinforced composite material. Graphene oxide and carbon naotubes are assembled into a nano-carbon mixed structure reinforcement with the high self-supporting property, and after resin matrix infiltration and polymerization, the carbon nanotube-graphene oxide mixed reinforced composite material is obtained; the porous carbon nanotube-graphene oxide reinforcement with the low density and the high specific surface area is prepared by taking 2-ethyl-4-methylimidazole as a bridge between the nanotubes and graphene oxide, and the reinforcement retains the respective characteristics of graphene oxide and the carbon nanotubes and is composited with multiple resin matrixes by serving as three-dimensional macroscopic continuous reinforcement with the high electricity conductivity and thermal conductivity, and then the multifunctional low-cost carbon nanotube-graphene oxide mixed reinforced composite material is prepared.