A newly developed method to prepare the ultrafine and size-controlled powders of TiB2 based on magnesium-thermic reduction was described. The preparation of TiB2 powders from TiO2 and B2O3 by magnesium-thermic reduction with MgO was examined in the temperature range from 500°C to 1000°C at Mg/TiO2 (molar ratio)=3 to 7 and at B2O3/TiO2=0.6 to 3 under flowing argon gas. The TiB2 was formed above 525°C. The TiB2 powders were washed with 10%NH4Cl water-solution, then 10%HNO3 water-solution, followed by water washing and drying. The average sizes of TiB2 powders thus obtained were in the range of 0.35-2.5 ftm with plate-like crystallite. The composition of TiB2 was approximately equal to the stoichiometry.