A　facile　approach　was　developed　to　simultaneously　functionalize　and　reduce　graphene　oxide　(GO)　with　9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide　(DOPO)-phosphonamidate.　To　achieve　stable　dispersion　and　effective　stress　transfer,　graphene　was　functionalized　by　polyethyleneimine　(PEI).　To　improve　the　fire　resistance　of　bare　graphene,　DOPO　was　grafted　on　the　surface　of　PEI-reduced　graphene　oxide　(PEI-rGO)　to　obtain　the　grafting　of　DOPO-phosphonamidate　on　the　graphene.　A　morphological　study　indicated　that,　due　to　the　good　interfacial　interaction　between　the　functionalized　graphene　and　epoxy　(EP),　functionalized　reduced　graphene　oxide　(f-rGO)　was　well-dispersed　in　the　host　polymer.　Incorporation　of　3.0　wt%　f-rGO　led　to　the　increased　char　yields　of　the　EP.　Moreover,　the　storage　modulus　and　glass　transition　temperature　were　improved,　respectively.　The　evaluation　of　combustion　behavior　demonstrated　that　the　peak　heat　release　rate　and　total　heat　release　of　f-rGO/EP　were　reduced　by　31%　and　34.3%,　respectively,　compared　to　those　of　neat　EP.　This　dramatically　reduced　fire　hazards　were　mainly　attributed　to　the　synergistic　effect　of　f-RGO.　On　one　hand,　DOPO-phosphonamidate　on　the　surface　of　GO　promoted　flame　inhibition　in　the　gas　phase　while　protecting　the　rGO　against　fire.　On　the　other　hand,　the　adsorption　and　barrier　effect　of　rGO　inhibited　the　heat　and　gas　release,　respectively,　promoting　the　formation　of　graphitized　carbons.　©　2018