It　has　been　desirable　to　create　biodegradable　polymer　materials　that　are　thermally　stable,　flame-retardant　and　mechanically　robust.　One　promising　strategy　is　to　develop　fire　retardant　polylactide　(PLA)　using　lignin　as　inexpensive　fillers,　but　existing　functionalized　lignin　cannot　improve　the　thermal　stability　of　PLA,　in　addition　to　unsatisfactory　fire　retardancy.　Herein,　we　report　a　lignin-derived　fire　retardant　(LF)　by　grafting　poly-phosphoramide　into　the　chemical　structure　of　lignin　waste　through　graft　polymerization.　The　results　show　that　with　8　wt%　of　LF,　the　final　PLA　shows　significantly　enhanced　thermal　stability　in　N-2.　Moreover,　the　resulting　PLA　achieves　a　satisfactory　UL-94　V-0　rating,　meeting　the　demanding　requirement　of　fire　retardancy　in　industries.　Additionally,　the　PLA/LF　composite　displays　increased　elastic　modulus　and　well-preserved　strength　and　ductility　of　pure　PLA.　This　work　provides　an　effective　strategy　for　creating　biobased　fire　retardant　additives　using　industrial　lignin　waste,　and　PLA　biocomposites　which　hold　great　promise　for　packaging,　fabrics,　electronic,　and　automotive　applications.