The invention discloses a composite current collector and a preparation method thereof. The method includes: coating mixture formed by nano carbon material, nano metal powder, metal catalyst, adhesive resin and organic solvent on one surface of a light foil, and rolling and pressing to form a conductive coating after drying; under a vacuum or protective gas atmosphere, performing high-temperature carbonization on the conductive coating to obtain the composite current collector. The method has the advantages that the conductive coating mixed by the nano carbon material, the nano metal powder, the metal catalyst and the adhesive resin, the adhesive resin is carbonized under catalyzing of the metal catalyst and under high temperature, and whisker-shaped carbon filaments which allow the nano metal powder and the nano carbon material to be connected, wrap the nano metal powder and the nano carbon material and is tightly combined with the light foil; no magnetic control sputtering equipment is needed, high equipment investment is avoided, no methane atmosphere is needed, and danger in production is lowered.