An 90 days feeding trial was conducted to estimate the adequate dietary vitamin C requirement of juvenile Wuchang bream (Megalobrama amblycephala) and its effect on on growth, physiological and biochemical, immunity and three HSPs mRNA expression. 540 healthy fish with initial body weight(6.40±0.05)g were selected and randomly divided into six groups and Vc supplemented at 0.2 ,33.4,65.8 ,133.7,251.5 and 501.5 mg/kg diet. After 90 days feeding, the growth performance, hematology and muscle physiochemical indexes were investigated. The results showed that the weight gains (WG) and specific growth rate (SGR) had an increasing trend with the increase of dietary vitamin C, the fish in 251.5 mg/kg and 501.5 mg/kg Vc group had significantly higher SGR then those in the control group (P<0.05); while the feed coefficient reduced with increasing of dietary vitamin C, but no significant difference were observed among dietary treatments (P>0.05). The fish body indices were not significantly different among groups, except the viscerosomatic index in fish with 120 mg/kg vitamin C was significantly higher then the control group (P<0.05). Compared with the control, total leukocytes count in fish with 65.8-501.5 mg/kg vitamin C, the contents of serum glutamic-oxaloacetic in fish with 65.8 mg/kg, and the contents of serum glutamic-pyruvicStransaminase in fish with 133.7 mg/kg and 501.5 mg/kg were significantly reduced (P<0.05). The contents of serum triglycerides and complement 3 in fish with 501.5 mg/kg, total superoxide dismutase activities in the musclr in fish with 133.7 mg/kg were significantly improved (P<0.05). Other indices, such as erythrocyte, hemoglobin, platelets,Salbumin and cooking loss of muscle were not significantly different between groups(P>0.05). Based on broken-line model analyses at this study, the minimum dietary vitamin C level is 150 mg/kg to get optimal WG.