Effects of single molecular and double molecular substituted phenolic chelating agents on scavenging of superoxide anions and hydroxyl radicals and inhibition of rat liver mitochondria lipid peroxidation induced by irradiation were studied. The phenolic chelating agents were shown to different extent to scavenge oxygen free radicals and to protect against radiation-induced lipid peroxidations, and their half inhibition concentrations (IC,50,) on hydroxyl radicals generation and lipid peroxidation were 1×10,-6,mol/L, which of scavenging of superoxide anions were 1×10,-3,mol/L. 7601 (CBMIDA) , 9501 and 9502 were the best among them. The free radical scavenging and antioxidant activities were close related to chemical structure and decorporated bioactivity.