The invention belongs to the technical field of proton exchange membranes of fuel cells and particularly relates to a preparation method of a high-temperature-resistant aminated graphene oxide/sulfonated polybenzimidazole proton exchange composite membrane. The preparation method comprises the step of carrying out in situ polymerization on tetramine monomers, non-sulfonated diacid monomers containing -O- flexible groups, sulfonated diacid monomers and aminated graphene oxide under nitrogen protection, so as to prepare the aminated graphene oxide/sulfonated polybenzimidazole proton exchange composite membrane. The composite membrane has good mechanical stability and heat resistance, and compared with purely sulfonated polybenzimidazole, the proton conductivity is greatly increased.