Juvenile yellow catfish Pelteobagrus fulvidraco （Richardson） with 18.0 g in body weight were stocked into 36 net cages of 60 cm ? 60 cm ? 120 cm each and fed semi-purified formulated feed containing 30%, 38% and 46% of dietary protein and supplemented with four levels of ascorbic acid-2-phosphate （AA） （0, 500, 1000, 1500 mg?kg^- 1 diet, ） at 22 ? 3 ℃ for 50 days. The results showed that the fish fed the formulated feed containing 38.0% - 40.0% dietary protein bad the maximal special growth rate （ SGR）, and protein efficiency ratio （PER） and the minimal feed coefficient （ FC）. The catfish had the maximal levels of total plasma protein, γ-globulin, and activities of lysozyme and the minimal activity of superoxide dismutase when fed 847, 850, 994 and 634 AA mg?kg^-1 diet. In the fish fed the formulated feed varying from 30% to 38% in dietary protein, the protein in muscles increased from 60.95% to 69.86%, and the lipid decreased from 29.27% to 21.69%, whereas the fish fed the formulated feed containing 46% dietary protein bad a decrease in protein （64.35 % ） and an increase in lipid （26.06 % ） levels in muscles. There were significantly higher saturated fatty acid levels （SFA） （ P 〈 0.01 ）and monounsaturated fatty acid levels（ P 〈 0.05）in museles in the fish fed the feed containing 38% dietary protein than those in the fish fed the feed containing 30% and 46% dietary protein. There were significantly higher linolenic acid and n - 3 polyunsaturated fatty acid （ n - 3 PUFA） levels in muscles in the fish fed the 38% and 46% （ P 〈 0.01, P 〈 0.05） dietary protein feeds than those in the fish fed the 30% dietary protein feeds. It was found.that there was significantly higher n - 3/n - 6 ratio in the 30% and 46% dietary protein groups than in the 38% dietary protein group. For yellow catfish juveniles, the optimal dietary protein and vitamin C levels have been considered as 35.58 - 40.60% and 600 - 800 mg? kg^-1, respectively.