To　improve　both　the　mechanical　and　thermal　properties　of　kaolin/polypropylene　(PP)　composites,　kaolin　was　modified　by　using　3-(trimethoxysilyl)　propylmethacrylate　(YDH-570)　as　a　coupling　agent　to　form　polymerizable　particle.　Styrene　was　radically　polymerized　through　the　immobilized　vinyl　using　benzoyl　peroxide　(BPO)　as　an　initiator.　Fourier　transform-infrared　(FTIR)　spectroscopy,　particle　size　distribution,　X-ray　diffraction　(XRD)　and　thermo-gravimetric　analysis　(TGA)　well　demonstrated　that　the　kaolin-polystyrene　particles　were　successfully　synthesized　via　in-situ　polymerization.　While　the　modified　kaolin　and　raw　kaolin　were　introduced　into　the　PP　matrix,　it　could　be　concluded　that　modified　kaolin/PP　composites　have　better　mechanical　and　thermal　properties　than　raw　kaolin/PP　composites,　and　these　improvements　were　attributed　to　the　desirable　dispersion　of　kaolin　in　PP　matrix.　©　2010.