The nanosized titania and TiO2/SiO2 particles were prepared by the microwave-hydrothermal method. The effect of physical properties TTIP/TEOS ratio and calcination temperature has been investigated. The major phase of the pure TiO2 particle is of the anatase structure, and a rutile peak was observed above 800 degrees C. In TiO2/SiO2 particles, however, no significant rutile phase was observed, although the calcination temperature was 900 degrees C. No peaks for the silica crystal phase were observed at either silica/titania ratio. The crystallite size of TiO2/SiO2 particles decreases as compared to pure TiO2 at high calcination temperatures. The TiO2/SiO2 particles show higher activity on the photocatalytic decomposition of orange II as compared to pure TiO2 particles.