[Objective] The aim was to clarify the antioxidative defense of glutathione( GSH) to ammonia stress. [Method] Cyprinus carpio were exposed to different ammonia levels: 0 mg / L( control),10 mg / L( low),20 mg / L( middle) and 30 mg / L( high) NH4 Cl,each ammonia level was randomly triplicate and sampled at 6,24 and 48 h,respectively.[Results]The results indicated that the content of GSH and activities of glutathione peroxidase( GSH-PX) and glutathione S-transferase( GST) increased significantly after expose...