Abstract: Based on SHS reductive reaction,TiB₂mixed powder was synthesized and the high-pure TiB₂ was obtained by acid-washing treatment．The effects of synthesis procedure and acid-washing conditions on the purity of TiB₂ powder were investigated,and the thermodynamics of acid-washing procedure for synthesized powder were analyzed．The experimental results showed that the chemical reaction of the TiO₂-B₂O₃-Mg system consisted of two parts．In the first step,the elements of B and Ti were reduced by Mg powder,secondly,the TiB₂ was formed by chemical combination of the two monomer elements．The purity of TiB₂ powder mainly depends on acid-washing conditions．With the concentration of hydrochloric acid and amount of excessive acid increasing and the acid-washing time prolonging,the purity of TiB₂ powder increase gradually．Moreover,with the acid-washing temperature rising up,the acid-washing velocity can be considerably quickened．