The oxygen consumption of different size Tilapia nilotica were measured andstudied under temperatures ranging from 21℃ to 26.5℃, within 24 hours in succession.The results are summarized as follows: At body weight 0.00306 kg, it is 250.76mg/kg/hr at temperaturo of 24℃; attwo-month old, body weight 0.04053 kg and 0.04289 kg, it is 136.58mg/kg/hr and154.48 mg/kg/hr respectively at 24℃; at three and half-month old, body weight0.07150 kg, it is 91.61 mg/kg/hr at 21℃; at fifteen-month old, body weight0.23300 kg and 0.43330kg, it is 67.90mg/kg/hr and 123.10mg/kg/hr respectivelyat 22.5℃ and 26.5℃; at twentyfour-month old, body weight 0.47200 kg and0.56830kg, it is 88.58mg/kg/hr and 111.58 mg/kg/hr at 22.5℃ and 26.5℃respectively. The experiments show that oxygen consumption of T. nilotica decreases as the ageor the body weight increases. This indicates that the younger fish require higheroxygen consumption than do the older ones, and the rate of oxygen consumption ofthe fish increases as the water temperature rises. The rates of oxygen consumption between the male and the female T. nilotica areshows no significant difference at the same size and same water temperature. The fish can survive in very low oxygen content waters, and its the asphyxiatingpoint is 0.07-0.23 mg/l.