Vitamin C, or ascorbic acid (AA), is important in growth and physiological functions of fish. Six soybean meal-based (SBM) diets containing 0, 125, 250, 500, 1000 and 2000 mg.kg^-1 of AA were fed to snakehead (6.6-6.7 g) for eight weeks in the laboratory. Survival, final weight, and specific growth rate (SGR) of snakehead in the 250 and 500 mg.kg^-1 treatments were significantly greater than those in the control (0 mg.kg^-1). Feed intake (FI), feed conversion ratio (FCR), and protein efficiency ratio (PER) also differed significantly. The requirement of AA for snakehead was calculated to be 277 mg.kg^-1. No abnormal backbones were observed during the experimental period. Erythrocyte count was significantly higher at 1000 and 2000 mg.kg^-1 than at 0 and 125 mg.kg^-1. Fish in 250 mg.kg^-1 had significantly higher leukocyte count than 0, 1000, and 2000 mg.kg^-1. A bacterial challenge test with Aeromonas hydrophila revealed that 500 and 1000 mg.kg^-1 had the lowest cumulative mortality. In an on-farm trial, SBM-based and commercial diets augmented with 0, 500, 750, or 1000 mg.kg^-1 AA were fed to C. striata for 23 weeks. Optimal results were obtained with SBM-based diets supplemented with 500 mg.kg^-1 AA, in terms of survival, yield, FCR, production cost and profit.