A new series of Schiff base ligands were synthesized by the condensation of 2-amino-5-mercaptan-1,3,4-thiadiazole and salicylaldehyde or 2,4-dihydroxybenzaldehyde and their derivatives with choroacetic acid, and further reaction with corresponding metal acetate to form metal complexes. The compositions and structures of the ligands and their complexes were characterized by elemental analysis, molar conductivities, electronic absorption spectra and infra-red spectra. Their inhibition rates to free radical, such as O2, were also tested. The results show that all of the obtained complexes display significant activities, among which the copper(II) complexes have the best inhibitive effects. A new series of Schiff base ligands were synthesized by the condensation of 2-amino-5-mercaptan-1,3,4-thiadiazole and salicylaldehyde or 2,4-dihydroxybenzaldehyde and their derivatives with choroacetic acid, and further reaction with corresponding metal acetate The compositions and structures of the ligands and their complexes were characterized by elemental analysis, molar conductivities, electronic absorption spectra and infra-red spectra. Their inhibition rates to free radicals, such as O2, were also tested. The results show that all of the obtained complexes display significant activities, among which the copper (II) complexes have the best inhibitive effects.