A mild solution route has been designed for the synthesis of uniform TiO₂/SiO₂ composite microspheres with octadecyltrimethoxysilane (C18TMS) and tetrabutyl titanate at low temperature via a self-assembly process. The TiO₂ composite microspheres consisted of TiO₂ nanoparticles with several nanometers in diameter; and the size and morphology of the composite microspheres can be well controlled by controlling the reaction conditions. Octadecyltrimethoxysilane and reaction temperature play key roles in the formation of the composite microspheres. In particular, the synthesized composite microspheres exhibit strong anatase phase stability and good performance on photodegradation of RhB dye from the pollutant solution. All the results reveal that the self-assembly strategy represents a facile method for controlling the crystallinity and size of TiO₂ photocatalysts and for their excellent photocatalytic activity, which is also of great importance to the potential applications in solar cells and lithium ion batteries etc.