The invention provides three-dimensional structure composite aerogel and a preparation method thereof. The three-dimensional structure composite aerogel is formed by ascorbic acid, copper nanowire, oxidized graphene and water, and the mass ratio of the ascorbic acid, the copper nanowire and the oxidized graphene is 2-20: 0.01-200:1. The ascorbic acid is added in mixed solution to effectively restrain oxidation of the copper nanowire in the chemical reduction co-assembly process, and the oxidation problem of the copper nanowire in the chemical reduction co-assembly process with the oxidized grapheme is solved; the diameter of the copper nanowire is small, and the surface energy is strong, so that the copper nanowire easily gathers in aqueous solution. The oxidized graphene, known as surfactant, is equipped with a unique two-dimensional structure and physical properties, and is capable of adsorbing the copper nanowire through the interaction with the copper nanowire, restraining gathering of the copper nanowire, and promoting dispersal of the copper nanowire to solve the problem of dispersal of the copper nanowire.