A series of novel polyimide composite films modified by silicone were synthesized from aminopropyl-end capped polydimethylsiloxane(PDMS), pyromellitic dianhydride(PMDA), and 4, 4’-oxydianiline(ODA) via thermal imidiazation. Films were analyzed and characterized by FTIR, XPS and SEM. The AO-resistant property of composite films was tested by ground atomic oxygen (AO) simulation devices. It was revealed that the AO denudation rate of composite films could be up to 6.69?0-25cm3/atom when the AO flux was up to 2.06?020atom/cm2. The AO-resistant property of composite films is about 4.5 times to pure polyimide films.