Flame　retardant　rigid　polyurethane　foam　(RPUF)　with　a　reactive　melamine-derived　polyol　(MADP)　and　9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide　(DOPO)　were　fabricated　through　free-rise　technique.　The　thermal　stability　and　fire　behaviors　of　RPUF　were　investigated　by　thermogravimetric　analysis　(TGA),　limiting　oxygen　index　(LOI),　and　cone　calorimeter.　In　comparison　with　the　results　of　RPUF　and　RPUF/MADP,　RPUF/MADP-DOPO　displayed　higher　compressive　strength,　owing　to　the　two　stiff　phenyl　groups　of　DOPO.　Moreover,　with　only　7.5　wt　%　MADP　and　7.5　wt　%　DOPO　loading,　the　MADP/DOPO　system　endowed　RPUF　with　enhanced　char　formation,　increased　LOI　value　of　28.5%　and　reduced　heat　release.　Scanning　electron　microscope　(SEM)　images,　X-ray　photoelectron　spectroscopy　(XPS)　analysis　and　Raman　spectra　of　the　char　residues　suggested　that　the　formation　of　compact,　continuous　char　layer.　The　thermal　degradation　was　characterized　using　thermogravimetric　analysis/infrared　spectrometry　(TG-IR)　and　chemical　structure　changes　during　the　thermal　degradation　were　monitored　by　real　time　Fourier　transform　infrared　(RT-FTIR),　these　results　demonstrated　that　the　partial　phosphorus　from　DOPO　remained　in　the　residual　char,　but　the　introduction　of　MADP　significantly　promoted　generating　more　stable　aromatic　structure　and　enhanced　the　strength　of　the　char　layer　formed.　Furthermore,　MADP　facilitated　the　formation　of　more　H2O　and　CO2　and　diluted　the　flammable　gases　in　gaseous　phase.　Based　on　the　analysis,　the　introduction　of　MADP/DOPO　can　endowed　excellent　flame　retardancy　to　RPUF　depending　on　bi-phase　flame-retardant　mechanism.　©　2018　Elsevier　B.V.