Abstract: The main flavonoids and their contents were qualitatively and quantitatively analyzed by HPLC-MS/MS method in the sawdust Larix olgensis var. koreana,which was taken as research object,and their antioxidant activities were also determined. The results showed that three kinds of flavonoids,namely dihydroquercetin(92.07%),aromadendrine(2.39%)and ergophenol(0.19%)were observed in L. olgensis var. koreana. Strong antioxidant activity against DPPH free radical were detected in both L. olgensis var. koreana flavonoids extract and dihydroquercetin,which were higher than BHT and the data reached 92.21% and 93.45% at concentration of 0.2 mg/mL,respectively. The strong activity by L. olgensis var. koreana flavonoids extract against ABTS free radical which reached 91.43% at concentration of 0.05 mg/mL were also observed,even the higher ABTS free radical clearance rate increasing to 93.45% was investigated with dihydroquercetin at concentration of 0.2 mg/mL. The weaker antioxidant capacity were revealed by citrin and eriodictin in DPPH and ABTS experiment,the data were both lower than 50%.