The invention discloses a preparation method of a graphene and aluminum oxide whisker co-reinforced copper-based composite material and a product thereof. The preparation method comprises the following steps: wet-grinding and mixing surface-modified aluminum oxide whiskers, surface-modified graphene and copper powder, and performing vacuum drying to obtain a mixture; then performing compression molding on the mixture to obtain a pressed blank; performing vacuum hot-pressing sintering on the pressed blank, cooling, and then performing hot isostatic pressing treatment on a sample to obtain the graphene and aluminum oxide whisker co-reinforced copper-based composite material, wherein the graphene and aluminum oxide whisker co-reinforced copper-based composite material comprises the followingcomponents in percentage by weight: 0.5-2.0% of the surface-modified aluminum oxide whiskers, 0.25-1.0% of the surface-modified graphene and the balance of the copper powder; and the weight ratio of the surface-modified aluminum oxide whiskers to the surface-modified graphene is (1-4): 1. The copper-based composite material prepared by the method can have excellent mechanical properties and relatively high density at the same time.