Nanosized pure Ti0₂ particles were prepared by hydrolysis of TTIP in the sodium bis ( 2 -ethylhexyl) sulfosuccinate (AOT) reverse micelles. TiO₂/SiO₂ nanoparticles were also prepared from TEOS as a silicon source and TTIP as a titanium source for comparison. Properties of these particles were characterized by TEM, XRD, FT-IR, BET, TGA and DTA. From XRD data, no significant rutile phase was observed even though the TiO₂/Si0₂ particles were calcined at 800℃. The presence of amorphous silica in TiO₂/SiO₂particle enhanced the thennal stability of Ti02 particle and resulted in the suppression of the phase transition from anatase to rutile. The crystallite size of prepared particles decreased and the surface area increased monotonically with an increase of the silica content. From FT-IR analysis, the band for Ti-0-Si vibration was observed and the band for Si-0-Si vibration increased with an increase of the silica content. The micrographs of TEM show that the TiO₂/Si0₂ nanoparticles have a spherical morphology with a narrow size distribution. In addition, TiO₂/SiO₂ particles have higher photocatalytic activity than pure Ti0₂ and the Ti0₂/Si0₂(90/10) particles show the highest activity on the photocatalytic decomposition ofp-nitrophenol.