Titania-silica composite nanoparticles were prepared by sol-gel-hydrothermal and sol-gel routes, respectively, and their physicochemical and photocatalytic properties were compared. The results of XRD, TEM and BET surface areas showed that sol-gelhydrothermal route led to anatase titania-silica composite nanoparticles with large specific surface area, but the sol-gel route tended to form mixture of anatase and rutile. The composite nanoparticles prepared by sol-gel-hydrothermal route had better thermal stability against phase transformation from anatase to rutile, agglomeration and particle growth than those prepared by sol-gel route. On the basis of XRD, FT-IR, XPS and 29 Si MAS-NMR, a strong interaction was found between SiO 2 and TiO 2 , and Ti-O-Si bonds formed during both the two routes. But more Ti-O-Si bonds formed in the composite nanoparticles prepared by sol-gelhydrothermal route than those prepared by sol-gel route. As a result, the titania-silica composite nanoparticles prepared by sol-gelhydrothermal route exhibited higher photocatalytic activity in decomposition of methylene blue than that prepared by sol-gel route, and it had excellent photocatalytic activity even after calcined at 1000 1C.