Abstract: The surface of sub-micron-sized antibacterial agent was modified with stearic acid and titanate coupling agent. The inorganic antibacterial agent used was TiO_2 containing Ag +. The results show that the surface of TiO_2 is modified from hydrophilic to hydrophobic. It has been demonstrated that the surface modification of the inorganic particles can improve the compatibility and adhesion with the organic matrix materials. The structure and morphology were characterized by IR, TEM etc. The content of Ag + was detected by XRFP. It shows that stearic acid and titanate coupling agent have been grafted in the TiO_2 surface and the surface of TiO_2 is modified from hydrophilic to hydrophobic. The grafting efficiency can improve to 0.92%. The antibacterial efficiency was tested according to the standard issued by Ministry of Health of China and the result for coliform was 99.7% with method of flask-surging.