Mirror carp Cyprinus carpio were fed diets containing different concentrations of olaquindox ( 0- 3200 mg ..kg - 1) for 12 weeks. Activities of two antioxidant enzymes such as superoxide dismutase ( SOD) and glutathion peroxidase ( GSH..px ) , levels of malondialdehyde ( MDA ) and total ant ioxidat ive competence ( T..AOC ) in hepatopancreas were determined every 3 weeks. SOD activities roughly increased with increasing olaquindox concentration, but didn.. t change greatly as feeding period was prolonged. Activities of GSH..px were not affected markedly by increasing olaquindox concentration and feeding period until above the dose of 1600 mg..kg- 1. Also were MDA contents influenced in general with the change of olaquindox concentration in feed, however, decreased gradually when the period was lengthened except for a do se of 3200 mg ..kg - 1 . T..AOC values declined with increasing olaquindox concentration and feeding period, and did to a very low level at above 1600mg..kg - 1Fromthese results, it can be concluded that ant ioxidant enzyme activities are induced more signif icantly at relat ively higher concentration of olaquindox than at lower concentration. Elevation of concentration of olaquindox in feed is accompanied by weakened antioxidative ability of carp.