The invention provides a preparation method of a copper/graphene composite material. The preparation method comprises the steps: firstly, preparing a graphene thin film on a rolled copper foil after cleaning and polishing by a chemical vapor deposition method, plating a SiO2/Si sheet with a layer of copper film with the thickness of 400-700 nm by a magnetron sputtering coater, and preparing a copper film/SiO2/Si sample; then, transferring the graphene thin film prepared by the chemical vapor deposition method to the surface of the copper film/SiO2/Si sample by a corrosion substrate method, toprepare a graphene/copper film/SiO2/Si sample; secondly, carrying out magnetron sputtering of the surface of the graphene thin film/copper film/SiO2/Si sample with a layer of copper film with the thickness of 450-550 nm, to obtain a copper film/graphene/copper film/SiO2/Si sample; finally, transferring the graphene thin film prepared by the chemical vapor deposition method to the surface of the composite material; and preparing and transferring graphene and sputtering copper thin films repeatedly, and finally obtaining the nanosandwich composite material with four layers of copper films and three layers of graphene thin films. The preparation method is simple, convenient to operate and low in cost, and has good application prospect.