The　flame-retardant　modification　of　rice　straw　fibers　(RSFs)　was　carried　out　to　solve　the　technical　problem　of　poor　fire-proof　performance　of　RSFs.　The　physical　and　mechanical　properties　and　thermal　insulation　properties　of　rice　straw　fiber　cement-based　composites　(RSFCC)　at　high　temperatures　were　characterized.　The　results　show　that　the　three　flame　retardants　affected　the　chemical　structure　of　RSFs.　The　thermal　stability　and　flame　retardancy　of　flame-retardant　RSFs　were　significantly　higher　than　that　of　non-flame-retardant　RSFs.　The　crystallinity　of　several　groups　of　modified　RSFs　increased　in　varying　degrees　compared　to　untreated　fibers.　The　massloss　rate　of　RSFCC　increased　with　the　increase　of　temperatures.　The　strength　and　thermal　conductivity　of　RSFCC　decreased　with　the　rise　of　temperatures.　The　strength　and　thermal　conductivity　of　the　composite　flame-retardant　modified　fiber　RSFCC　at　high　temperatures　were　significantly　higher　than　those　of　the　non-flame　retardant　modified　fiber　or　the　single　flame　retardant　modified　fiber　RSFCC.