In the paper, titanate and aluminate-coupling agents were used to the surface modification of ultrafine inorganic antibacterial particles (UIAP) by dry mixing and solution methods. Several characterization methods were carried out to qualitatively and quantitatively analyze the results of surface modification such as Fr-IR, water-absorbability and viscosity methods. The modified UIAP was added into PP to prepare antibacterial composites. The SEM showed that the surface-modified UIAP was well dispersed in PP and the average particle size was lower than 0.5 mum. Solution method has better effect on the surface treatment of inorganic particles compared with dry mixing method. The mechanical properties of composites were tested, and the results approved that coupling agents could improve the mechanical properties of composites in a certain range. The experimental results indicated that the optimal content of titanate- and aluminate-coupling agents were 1.5 and 2.0-3.0 wt.%, respectively. Examination of antibaterial property proved that surface modification had no influence on antibacterial capability of UIAP; moreover, PP/UIAP composites have good antibacterial property and broad-spectrum antibacterial capability as well as UIAP. (C) 2004 Elsevier B.V. All rights reserved.