TiB2/TiC　nanocomposite　powder　was　synthesized　by　ball　milling　the　industrial　grade　Ti　powder　and　B4C　powder.　The　results　show　that　the　milling　atmosphere　plays　a　crucial　role　in　the　synthesis　of　TiB2/TiC.　After　5　h　milling　under　an　appropriate　argon　protection,　a　solid　state　reaction　between　Ti　and　B4C　occurs　resulting　in　the　formation　of　TiB2/TiC　phases.　With　increasing　of　the　milling　time,　the　crystal　size　of　synthesized　TiC　is　decreased　to　about　10　nm　while　the　crystal　size　of　TiB2　is　slightly　larger.　When　the　air　is　introduced　in　the　milling　process,　a　large　amount　of　TiN　and　TiO　will　occur　in　the　milled　product.