Surface-modified　ultra-fine　brucite　powder　is　a　kind　of　environment-friendly　fire-retardant　of　polymer.　The　ultra-fine　brucite　powder　was　surface-treated　with　two　kinds　of　silane　(A-174　and　FR-693),　and　then　filled　into　polypropylene　(PP)　as　a　kind　of　fire-retardant　aimed.　The　effect　of　modification　by　silane　on　the　properties　of　PP/brucite　composite　material　was　studied.　The　effect　and　modification　mechanism　were　investigated　by　means　of　Fourier　transfer　infrared　analysis,　scanning　electron　microscopy　of　brucite　powder　and　the　fresh　new　surface　of　PP/brucite.　The　results　show　that　the　optimal　dosage　of　brucite　powder　for　silane　A-174　and　silane　FR-693　is　1.5%　and　1.0%　in　mass　respectively　and　the　temperature　of　surface　treatment　is　80°C.　It　indicates　that　the　surface　modification　can　enhance　the　izod　impact　strength　of　PP/Mg(OH)2　composite　material　by　0.3　kJ/m2,　the　bend　modulus　about　30%,　and　the　retardant　degree　is　enhanced　to　V-0　from　V-1.　The　tensile　strength　of　the　composite　material　surface　modified　with　silane　FR-693　can　be　increased　1　MPa.　The　bending　strength　and　elongation　at　break　of　the　material　are　not　improved　by　both　silane.