Abstract: In this study, cold tolerance in different weight stages of NEW GIFT Nile tilapia（Oreochromis niloticus ）were investigated by measuring their Semi-lethal low temperature and cooling degree hours et al, in the condition of indoor artificial cooling. The results indicated that the cold tolerance ability of NEW GIFT Nile tilapia was significantly enhanced with weight growing. The LT50 values of the four stages were: 9.72℃, 8.80℃, 8.70℃, 7.86℃ and the CDH values were 952.30 h, 1211.90 h, 1280.70 h, 1522.90 h. The correlation analysis and multiple comparisons among LT50 values and CDH values showed that the stage Ⅳ were significantly different from other stages（P<0.01）, which means that its cold tolerance ability is relatively stronger than that of the other stages, while the LT50 values and CDH values of the rest stages showed no statistical difference among themselves（P >0.05）. Therefore, tilapia of higher degree development also had a good cold tolerance.