The invention discloses a graphene composite material and a preparation method thereof. The graphene composite material has a multi-level core shell coating structure, wherein the nanometer silicon isused as the core, the graphene is used as the first coating layer, the carbon is used as the second coating layer, the surface of the nanometer silicon is coated with the graphene, and the surface ofthe graphene is coated with the carbon. The graphene has high conductivity, mechanical strength and flexibility, and provides a conductive network, an elastic space and a folded structure for the nanometer silicon, thereby being good for inhibiting the damage caused by the volume expansion of the silicon; the carbon can maintain the internal structure stability of the composite material, and prevent the composite electrode material from agglomerating and falling down. The composite electrode material has better stability and conductivity performance when being used for a lithium ion battery.The preparation method is simple in reaction and easy to control, and has a extensive application prospect.