The invention relates to a preparation method for a polyimide/oxidized graphene nanocomposite film, and belongs to the technical field of preparation of functional polymer materials. The preparation method comprises the following steps: performing ultrasonic even dispersion on the oxidized graphene in an organic solvent to obtain an oxidized graphene sheet suspension, wherein per ml of the oxidized graphene sheet suspension contains 1.3*10<-5>-1.3*10<-4>g oxidized graphene sheets; introducing nitrogen for carrying out deoxidization protection, adding diamine monomers into the suspension, mechanically stirring until full dissolution is achieved, adding dianhydride monomers, the moles of which are equal to that of the diamine monomers, in batches, and mixing for one to six hours under the ice bath conditions, so as to obtain polyamide acid/oxidized graphene composite solution; pouring the polyamide acid/oxidized graphene composite solution onto a die, removing the organic solvent, performing gradient temperature rise within 100-300DEG C, and carrying out thermal imidization to obtain the polyimide/oxidized graphene nanocomposite film.