Effect of heated effluent released from the Tarapur Atomic Power Station, India were investigated by analyzing the level of antioxidant enzyme activities on Nerita oryzarum. Seasonal variation of antioxidant enzyme (LPO, CAT, SOD, GPx and GST) were determined at six location. CAT increases in the pre-monsoon season (range of 0.12 to 2.1 mM of H2O2 consume/min/mg of protein) and LPO activities also increasing trend (range of 0.4 to 2.3 nM of MDA/min/mg) during same pre-monsoon at NIII and SII respectively. Enzyme values encountered high during pre-monsoon, which indicating that increased in temperature is resulting in increased activities. In experimental condition also (300C, 350C, 400C and 250C as control), antioxidant enzyme activities were in increasing trend due to raises of water temperatures. Present study was prima facie work related to physiological response of N. oryzarum related to heated effluent released from atomic power station and useful as baseline information for future research work.