Abstract: Cadmium-selenide quantum dots (CdSe QDs) were prepared by the hydrothermal method, and the CdSe QDs were doped in nano-TiO2 by the sol-gel method. Photo-catalytic property and micro-structure of the nano-composite were studied and characterized by various methods. It was shown that: ① CdSe QDs were doped and enters into nanoparticles of TiO2 during calcination in its prepartion to form nanocomposite;② the photo-absorptivity of TiO2 was enhanced, and its photoabsorption capacity in the visible region was improved;③ inherent crystal structure of TiO2 was transformed into mixed crystal structure of 2 crystal-phases during the calcination process, and this phenomenon was believed to be beneficial to improve its activity of photo-catalysis. In addition, the photocatalytic property of the nanocomposite was improved further by the synergetic action of the surface-electronic structure and the adsorptivity capacity of the nano-composite.