The invention discloses a preparation method of a graphene-copper oxide three-dimensional foam composite material. The preparation method comprises the following steps: step 1) dissolving raw materials, namely graphene oxide and copper salt, in water according to a certain mass ratio and uniformly mixing; step 2): separating the graphene oxide from the well mixed liquid, obtained in the step 1, by centrifugation or suction filtration and washing with water or alcohol; step 3) re-dispersing the product, obtained in the step 2, into a water solution, and then performing freeze-drying treatment on the product; and step 4) performing heat treatment on the product, obtained in the step 3, in air or oxygen to get the graphene-copper oxide three-dimensional foam composite material, wherein the heat treatment temperature is 150-800 DEG C, and the heat treatment time is 10s-10h.