The invention relates to a graphene airgel-supported nano-metal or metal alloy catalyst and a preparation method thereof, which belongs to the field of nano-material application and catalytic technology, and is characterized in that: graphene oxide and metal compounds are used as precursors, and a continuous reduction method is adopted , to obtain small-sized nano-metal and nano-metal alloy particles loaded three-dimensional porous graphene airgel catalyst. In the catalyst, the types of nano-metals and nano-metal alloys are selected from: Pt, Au, Ag, Pd, Ru, Rh, Pb, Fe, Co, Ni, Ir, Cu, etc.; the types and proportions can be arbitrarily matched. The size of the nanoparticles is about 2-6 nm, and they are evenly distributed on the graphene sheet. At the same time, graphene is assembled into a three-dimensional porous airgel structure with an average pore size of 1-2 microns, which can have a high specific surface area, high electron transport and mass transport rate, and prevent the agglomeration of graphene and nanoparticles. The composite material has excellent catalytic performance, and the components of the catalyst can be selected according to different needs.