The invention relates to a carbon nanotube-graphene composite material and a preparation method thereof. The preparation method comprises the following steps: (1) preparing a graphene/template composite by using a chemical vapor deposition method; (2) dispersing the composite in deionized water, adding a mixed solution of ferric nitrate and ammonium molybdate, stirring, and dropwise adding ammonia water to obtain a mixed solution, wherein the molar ratio of the ferric nitrate to the ammonium molybdate is 1: (0.01-10), and the mass percentage concentration of the ammonia water is 25-30%; and (3) carrying out suction filtering and drying on the mixed solution, and calcining at the temperature of 300-700 DEG C to obtain a catalyst for preparing the carbon nanotube-graphene composite material. In the preparation method, two-time chemical vapor deposition processes are utilized, and structure features and nitrating situation of graphene and carbon nanotubes are controlled.