Abstract: The process of Chemical Vapor Deposition (CVD) coating was investigated in the rotating reactor. Base on this ,TiO2 was coated on A12O3 particles by using hydrolysis reaction of Ti(OC4H9)4, and the mechanism of the coating process was studied. The results indicated that : (1) The coating film of TiO2 on A12O3 was compactness and uniform, and the coating quantity of TiO2 was about 0. 1%-10%; (2) The coated TiO2 was amorophous at low reaction temperature and was anatase at reaction temperature higher than 673K, the amorophous TiO2 could be translated to anatase by high temperature heat treatment; (3) Nucleation and film formation co - existed in the coating process, and nucleation could be promoted by controlling the concentration of reactant.