The purpose of this study was to evaluate the effects of dietary carbohydrate-to-lipid (CHO:LIP) ratios on growth performance, plasma biochemical indexes, pyruvate kinase (PK) and phosphoenolpyruvate carboxykinase (PEPCK) activity and mRNA expression in liver of juvenile GIFT Oreochromis niloticus. Five isonitrogenous and isoenergetic diets were formulated to contain various CHO:LIP ratios ranging from 1.5 to 16.5. Each diet was tested in three replicates of fish[initial weight:(6.77±0.14) g] for 8 weeks in the recirculating aquacultural system. The results indicated that specific growth rate (SGR), weight gain rate (WGR), protein efficiency ratio (PER) increased significantly as dietary CHO:LIP varied from 3.9 to 7.0, while feed conversion ratio (FCR) showed the opposite variation trend. Crude lipid content of whole body decreaced as dietary CHO:LIP ratios increased, and was at the lowest level in 16.5 group, which was significantly decreased only compared with 1.5 group. Plasma concentrations of triglycerides and total cholesterol also significantly decreased in 16.5 group. However, serum glucose increased significantly as CHO:LIP ratios increased. High dietary carbohydrate significantly enhanced the activities and mRNA expression of liver PK, while the effects of high carbohydrate on the activity and mRNA level of liver PEPCK were in a contrary tendency. Based on the second-order polynomial regression analysis of SGR, the optimal dietary carbohydrate and lipid contents for fingerling GIFT O. niloticus were 49.69% and 9.53%, respectively, with a corresponding dietary CHO:LIP ratio of 8.4.