To improve the atomic oxygen (AO) resistance of the spacecraft resin matrix material, inorganic silica nanoparticles were filled into the epoxy resin. Samples of the epoxy/silica nanocomposites were prepared and AO exposure experiments were conducted in a ground-based AO effects simulation facility. The samples exhibited significantly less mass loss and erosion yield than the corresponding pristine epoxy resin. Analysis of the surface morphology, composition and chemical structures showed that some organic structures still resides on the nanocomposites surface after the AO exposure experiment. The silica nanoparticles and the organic structures could serve as a barrier to resist further erosion.