Kinetics of second phase Ba6Ti17O40 formation in the mixture of BaTiO3 and excess TiO2 were studied by high-temperature X-ray diffraction method. The reaction curves were obtained at various temperatures for the formation of Ti-rich phase Ba6Ti17O40, and the reaction rate constant K and the activation energy Q were calculated. Finally, the mechanism of second phase Ba6Ti17O40 formation and the effect of excess TiO2 are discussed.