The invention discloses a polystyrene-based high heat conduction composite material and a preparation method thereof. The polystyrene-based high heat conduction composite material mainly consists of graphene nano pieces and polystyrene in a compounded manner, wherein the mixing mass ratio of the graphene nano pieces to the polystyrene is 1 to (10-100). The preparation method comprises the following steps: dissolving graphene nano pieces (GNP) and polystyrene (PS) which are synthesized through liquid-phase stripping into N,N-dimethyl formamide (DMF) respectively at the room temperature so as to obtain solutions of PS/DMF and GNP/DMF, mixing the two solutions, continuously stirring for at least 30 minutes, and continuously stirring till a solvent is completely volatilized; and finally performing hot-press molding on the obtained PS/GNP composite material, thereby obtaining the circular high heat conduction polystyrene composite material.