Abstract: A 42-d experiment was conducted to investigate the effect of upstream exercise and replacement of dietary fish oil by sunflower seed oil on the growth and body composition of GIFT Oreochromis niloticus. Three diets which contained 100% fish seed oil (A), 50% fish seed oil + 50% sunflower seed oil (B) and 100% sunflower seed oil (C) as well as two exercise intensity levels (0 BL · s^-1 and 1.5 BL · s^-1) were designed, so there were totally six treatment groups (0A, 1.5A, 0B, 1.5B, 0C, 1.5C) and three replicates in every treatment group. The results show that there was no significant difference (P>0.05) in survival rate among different groups. The highest specific growth rate was (4.96±0.02)% · d^-1 in Group 1.5B, significantly higher than that in the other groups(P < 0.05). Upstream exercise significantly improved the crude protein level in tilapia′s muscles (P < 0.05), with the highest increases of 10.25% and 7.74% in red and white muscles, respectively. Upstream exercise had no significant effect on polyunsaturated fatty acids (PUFA) in muscles and whole fish (P>0.05).The red muscles′ PUFA in Group B and Group C was significantly higher than that in Group A (P < 0.05), and no significant difference was found between Group B and Group C. Therefore, sunflower seed oil could partly or completely replace fish oil in diet with no significantly effect on the growth and body composition of GIFT O.niloticus, but upstream exercises significantly improved its muscles′ protein contents.