Abstract: To clarify the effects of vitamin C supplement in diet from different sources on the growth performance and tissue vitamin C content of Cyprinus carpio,four levels of coated-ascorbic acid(CAA)or ascorbic acid polyphosphate(LAPP)(50,100,150,and 200 mg/kg,vitamin C effective content in diet)were used.The experiment period was 60 d.The results showed that the optimal vitamin C effective content of LAPP and CAA requirements were 100~200 mg/kg diet and 150~200 mg/kg diet in koi juveniles,respectively.The fish groups of 150 mg(LAPP)/kg diet and 200 mg(CAA)/kg diet had the maximal vitamin C content in muscle and liver.And the liver vitamin C concentrations were higher than that of the muscle vitamin C concentrations.In conclusion,LAPP had advantage over CAA in promoting the growth of Cyprinus carpio.