Abstract: To investigate the effect of dietary vitamin E (VE) on serum complement C3 and C4,and the change of the complement under acid-stress in juvenile soft-shelled turtles (Pelodiscus sinensis),total 72 animals of one control group ? and five experimented groups (Ⅰ,Ⅱ,Ⅲ,Ⅳ and Ⅴ) were fed with VE supplementation at the dosages of 0,50,250,500,1000 and 5000 mg/kg diets,respectively.After feeding 4 weeks,half turtles per group were treated with acid stress for 24 h,and then the levels of their serum complement C3 and C4 were analyzed by transmission colorimetric method.The results showed that C3 levels in Ⅱ,Ⅲ and Ⅳ were significantly higher than that of C,and C4 levels in Ⅰ and Ⅱ were distinctly higher than that of C;C3 and C4 levels of both C and Ⅰ in stressed turtles had significant decreases compared with non-stressed ones,while the other four groups had no significant changes.Those suggest that VE seems to have an upper and lower threshold for improving levels of serum complement C3 and C4 in juvenile turtles,and acid stress decreases the levels,while the high dosage VE can withstand this decline.