Abstract: Ultra-fine BaTiO 3 powder with high tetragonality is the key material for the next generation of multilayer ceramic capacitors. In this paper, effects of medium size of the sand-milling and the phase of the raw TiO 2 on the reaction activity and dielectric properties of the product were investigated, and ultra-fine BaTiO 3 powder with high tetragonality was synthesized via the sand-milling process. Field emission scanning electron microscope images and X-ray photoelectron spectroscopy showed that the fine sand-milling media was more effective in crushing raw materials and mechanical activation. Raman spectroscopy and X-ray diffraction pattern proved that the anatase phase of TiO 2 was transformed into TiO 2 -II phase and rutile phase successively during the sand-milling process. Derivative thermogravimetry and X-ray diffraction analysis proved that fine sand-milling media was better at lowering the reaction temperature and inhibiting the formation of Ba 2 TiO 4 . The high resolution transmission electron microscopy image revealed that the formation of BaTiO 3 is a process by which Ba 2＋ diffuses into the TiO 2 lattice. The anatase TiO 2 /BaCO 3 mixture were sand-milled for 4 h, using ZrO 2 balls with a diameter of 0.1 mm, and calcined at 1 100 ℃ for 3 h. Then a well-dispersed BaTiO 3 powder with an average particle size of 186 nm and tetragonality of 1.009 2 was obtained. Sintered at 1 250 ℃, the density of the ceramic derived of as-prepared powder was 96.11%, and the peak value of the dielectric constant at the Curie point (137.8 ℃) was 8 677.