Abstract: The D-chiro-inositol was obtained by ultrasonic extraction from tartary buckwheat. The total D-chiro-inositol content was measured by sodium periodate oxidation method.The D-chiro-inositol was purified by activated carbon column.The composition of D-chiro-inositol extractions were analyzed by high performance liquid chromatography ( HPLC) method.Moreover, the reducing power of D-chiro-inositol extractions on DPPH, hydroxyl radicals and superoxide anion free radical in vitro was measured.Results showed that the content of crude D-chiro-inositol extractions in tartary buckwheat only attained0.129%, however, the content of purified buckwheat D-chiro-inositol by actived carbon column could be achieved 27.26%.The antioxidant ability of D-chiro-inositol extractions had higher DPPH free radical, superoxide anion free radical and hydroxyl free radical scavenging effects as well as good reducing capacity.Besides, the antioxidant ability of purified product was better than crude extracting from tartary buckwheat.