A 3-week feeding trial was conducted to determine the optimal dietary vitamin C requirement of largemouth bass (Micropterus salmoides) larva [(1.2±0.3) mg]. Five practical diets were formulated to contain 0 (V0), 200 (V200), 400 (V400), 800 (V800) and 1 600 (V1600) mg/kg vitamin C. Each experimental diet was fed to triplicate groups of fish to apparent satiation seven times a day. At the end of the experiment, the results showed that the final body weight, weight gain rate and specific growth rate increased with the increase of dietary vitamin C level, and then tended to be stable, with the highest values in VC400 group. Weight gain rate (WGR) and specific growth rate (SGR) markedly increased with increasing dietary vitamin C supply and then leveled off while body ASA concentration continued to increase with increasing dietary vitamin C supply. Vitamin C supplementation not only increased antioxidant capacities [activity of catalase (CAT)], reduced glutathione content (GSH), superoxide dismutase (SOD) and immunocompetence [complement C3, complement C4 and lysozyme(LZM) concentration)] of the larva, but also decreased lipid peroxidation (malondialdehyde (MAD) concentration) in the body. Broken-line analysis showed that the optimal dietary vitamin C requirement of M. salmoides was 421.2 mg/kg based on WGR. In practical production of largemouth bass larvae, 420 mg/kg of dietary vitamin C should be recommended to maintain normal physiological function.