Abstract: The poor atomic oxygen (AO) resistance of standard polyimide (PI) films significantly limits their applications on low Earth orbit (LEO) spacecraft surfaces. To fabricate AO-resistant polymer films, a combined approach involving chemical copolymerization and physical blending was employed. For chemical copolymerization, a polyhedral oligomeric silsesquioxane (POSS)-containing PI matrix was synthesized using diaminobenzamide isobutyl-POSS (DABA-POSS), a POSS-functionalized aromatic diamine precursor. For physical blending, trisilanolphenyl-POSS (TSP-POSS) was incorporated as a filler into the matrix. The resulting POSS-PI-30 film (with 30 wt% DABA-POSS) exhibits an AO erosion yield (E_y) of 1.64×10^-26 cm³·atom^-1 after exposure to AO irradiation with a fluence of 2.51×10²¹ atom·cm^-2, two orders of magnitude lower than that of conventional Kapton^® (PMDA-ODA PI) films. This study systematically documents AO erosion data from diverse POSS-based modification strategies, providing a quantitative reference for the design and optimization of anti-AO materials, and has basic data support value for the material screening of LEO spacecraft.