The invention relates to a preparation method for a nano metal oxide graphene composite material. The preparation method comprises the following steps: preparing graphite oxide aqueous dispersion from graphite oxide and water; throwing the graphite oxide aqueous dispersion into a ball-milling tank of a ball mill; adding nitrate and performing ball milling, wherein the nitrate is selected from one of or a mixture of more of silver nitrate, cobalt nitrate, manganese nitrate, ferric nitrate, nickel nitrate, bismuth nitrate, copper nitrate, cerium nitrate, vanadium nitrate, chromium nitrate, titanium nitrate, beryllium nitrate and vanadium nitrate; and after ball milling, dispersing the mixed liquid obtained by ball milling by using a proper amount of deionized water, standing and layering, filtering out precipitate, washing and drying. The preparation process is simple; the yield is high; the scale is easy to enlarge so as to realize industrialized production; the preparation process is environment-friendly; and in the prepared composite material, the nano metal oxide has the particle size of less than 50 nm, is uniform in size and is dispersed on the surface of graphene uniformly, the thickness of the graphene sheet is between 1 and 10 carbon atoms, and a good crystal structure is obtained.