Abstract: We conducted an 8-week feeding experiment by designing 6 kinds of feed (addition levels of betaine: 0, 0.05%, 0.10%, 0.20%, 0.30%, 0.40%)to investigate the effects of dietary supplementation of betaine on the growth, nutritional components, serum biochemistry and enzyme activity on liver of juvenile Rachycentron canadum. The results show that when the addition level is 0.05%, the weight gain (WG) and specific growth rate (SGR) reach the maximum; the condition of liver is the best; the protein content is the highest in both whole body and muscle. When the addition level is higher than 0.20%, the condition factor (CF) shows a negative correlation with the level of dietary betaine. Hepatosomatic index (HSI) of each group is significantly lower than that of the control (P < 0.05), and the lipid mass fraction (except for 0.10% group) is lower than that of the control. The concentration of triglyceride (TG) in serum is higher than that of the control, showing an "increase-decrease" trend. The activity of glutamic-pyruvic transaminase (GPT) of all groups are significantly lower than that of the control (P < 0.05). The results indicate that dietary supplementation of betaine can improve the growth and lipid metabolism for R.canadum, doing good to reduce the lipid of the fish.