Abstract: A series of graphene oxide/polyimide (GO/PI) composite films with excellent atomic oxygen (AO) resistance property was prepared by simple mechanical mixing (i.e. ball milling) of GO and PI followed by thermal compression. With a tiny addition of GO (0.5wt%), AO resistance property of GO/PI composite films with 0.5wt% GO addition is improved by approximately 17.9%, compared to the pure PI film. GO/PI composite films with 0.5wt% GO addition demonstrate excellent thermal stability and mechanical properties. The 5% mass loss temperature (T_d5) in nitrogen is 519.4℃, 14.7℃ higher than that of the pure PI film; the tensile strength and Young's modulus are 111.9 MPa and 2.1 GPa, 4.3 MPa and 0.1 GPa higher than those of the pure PI film, respectively. Compared to in situ polymerization used to fabricate GO/PI composite films, our method is much easier to operate and control, which makes it possible to manufacture GO/PI composite films with excellent comprehensive properties on a large scale.