The invention discloses a graphite composite material, and a preparation method thereof. The preparation method comprises following steps: S1, a plurality of graphite flakes are glued layer by layer with a resin so as to obtain a block with a thickness equals to or larger than 3mm, and heating curing molding is carried out; S2, laser cutting or line cutting is adopted to cut the block into a plurality of graphite laminated structures along the direction vertical to the plane of the graphite flakes; and S3, the surfaces of the graphite laminated structures are subjected to polishing so as to obtain the graphite composite material. The preparation method is capable of realizing high-efficiency large-scale production of the graphite composite material which is capable of dissipating heat in the vertical direction.