In　this　work,　a　novel　sulfur-based　flame　retardant　(SA-M)　was　synthesized　by　the　self-assembly　of　melamine　and　sulfamic　acid.　The　chemical　structure　of　SA-M　was　fully　characterized.　SA-M,　in　company　with　Al2O3,　was　then　introduced　into　polyamide　11　(PA　11)　by　melt　compounding　in　order　to　improve　the　fire　resistance　of　the　polymer　substrate.　The　observation　by　scanning　electron　microscopy　(SEM)　and　electron　probe　microanalysis　(EPMA)　indicated　the　well　dispersion　of　SA-M　in　PA　11　matrix.　The　fire　performance　of　PA　11　composites　was　evaluated　by　limiting　oxygen　index　(LOI),　vertical　burning　(UL-94),　and　cone　calorimeter　tests,　respectively.　The　results　showed　that　the　presence　of　17.5%　SA-M　and　2.5%　Al2O3　increased　the　LOI　value　from　22.4%　to　30.9%,　upgraded　the　UL-94　rating　from　no　rating　to　V-0,　significantly　eliminated　the　melt　dripping,　and　decreased　the　peak　heat　release　rate　from　1024　to　603　kW/m(2).　The　thermal　behaviors　were　investigated　by　thermogravimeric　analysis　(TGA)　and　TGA-Fourier　transform　infrared　spectroscopy　(FTIR).　It　was　suggested　that　SA-M　took　effects　mainly　in　gas　phase　by　diluting　the　combustible　fuel,　leading　to　the　improvement　of　the　fire　resistance　of　PA　11.