Extensive　application　of　epoxy　resins　(EPs)　is　highly　limited　by　their　intrinsic　flammability.　Combining　EPs　with　nanoparticles　and　phosphorus-nitrogen　flame　retardants　is　an　effective　approach　to　overcome　the　drawback.　In　this　work,　simultaneous　incorporation　of　octa-aminophenyl　polyhedral　oligomeric　silsesquioxanes　(OapPOSS)　and　polyphosphazene　into　EP　was　reported　for　the　first　time.　Significantly,　reduced　peak　of　heat　release　rate　and　UL-94V-0　rating　were　achieved　by　tuning　suitable　ratios　of　polyphosphazene　and　OapPOSS　for　EP　composites.　During　combustion,　polyphosphazene　promoted　char　formation　and　released　nonflammable　gases　such　as　CO2,　NH3,　and　N-2　to　dilute　oxygen　concentration　and　cool　pyrolysis　zone.　Moreover,　numerous　phosphorus-containing　species　acting　as　free　radical　scavengers　were　generated　during　degradation.　Silicon　dioxide　evolving　from　OapPOSS　protected　char　residues　from　thermal　degradation.　This　study　provides　a　novel　method　to　fabricate　high-performance　flame-retardant　EP　composites,　which　have　potential　applications　in　the　field　of　electrics　and　electronics.