Abstract: The 70% ethanol was used to extract the bibenzyl compounds from Dendrobinm denneanum, after HPD-300 macroporous resin purification, the bibenzyl compounds was obtained. The ability of removing AAPH·, DPPH·, superoxide anion radical and hydroxyl radical by the bibenzyl compounds solution were determined through oxygen radical absorbance capacity ( ORAC) , DPPH method, pyrogalbl autoxidation method and Fenton reaction.Results showed the activity of bibenzyl compounds from Dendrobinm denneanum and vitamin C with ORAC as index, the results were:0.33, 0.21mg /L ( scavenging AAPH·) , respectively.Antioxidant activity of bibenzyl compounds from Dendrobinm denneanum and vitamin C with EC 50 as index, the results were:62.89, 3.44mg /L ( scavenging DPPH) , respectively;408.10, 14.04mg /L ( scavenging O-2 ·) , respectively; 7.86, 1.89mg /mL ( inhibiting ·OH) , respectively.Compared with vitamin C, the clearance rates of AAPH·were higher in the bibenzyl compounds from Dendrobinm denneanum, could scavenge DPPH and superoxide anion radical and inhibit hydroxyl radical.The ability of removing radical showed a dose-effect relationship within the scope of the drug concentration.