The present invention discloses serial nano titanium compositions in core-shell structure and their preparing process. Through homogeneous precipitation process, the precipitation reaction and chemical processing are completed in one step. Transmissive electronic microscope detection shows that the initial particle has size of 30-80 nm; X-ray diffraction detection shows the crystal grain size of 10-30 nm; X-ray electronic energy spectrum analysis shows the oxide of Si or Al is concentrated mainly on the surface shell layer; and precipitation performance analysis shows that the serial nano titanium compositions in core-shell structure have slow precipitation speed in deionized water and have dispersivity greatly superior to nano titania prepared in the same process.