The effect of the KH-550 type silane coupling agent on the properties of polypropylene (PP)/brucite (BC) composite was stccudied. X-ray diffraction, scanning electron microscope, and polarization optical microscope indicated that morphology structure of PP changed with the addition of KH-550, which activated the heterogeneous nucleation centers on BC surface, which made the distribution of the spherulite diameter become narrow and uniform, and improved the dispersibility of BC in the matrix. Therefore, KH-550 enhanced the interfacial adhesion of matrix-filler and improved the compatibility of the PP/BC composite, when KH-550's content was 2.9% the tensile strength and impact strength increased approximately by 90% and by 30%, respectively than PP/BC. Flow tests and IR proved that some reactions took place between BC and H-550. All the investigations showed KH-550 was a proper coupling agent in the PP/BC composite. (C) 2007 Wiley Periodicals, Inc.