Chemiluminescence method was used to measure: (1) active oxygen species generation induced by respiratory burst of polymor-phonuclear leucocytes (PMNs) from human blood stimulated with phorbol myristate acetate (PMA); (2) superoxide (O2) induced by xan-thine-xanthine oxidase system; (3) hydroxyl radicals ( ? OH ) generated by Vit C- Cu2+- zy-mosan; (4) the release of hydrogen peroxide (H2O2). Effects of polydatin IV on these active oxygen species were observed. The resultsshowed early stage of respiratory burst of PMNs was inhibited,but the later stage was delayed by polydatin IV, (2), (3) adn (4) were scavenged by polydatin IV and their median inhibitory concentrations (IC50?mol ? L-1) were 14.6,29.6 and 13.0 respectively. The results suggested that polydatin IV was a scavenger.