The purpose of the study was to determine the optimized biotin levels in corn-soybean meal diet for the growth performance and some immune indices in weaned piglets challenged with porcine circovirus type 2 (PCV2). Fifty four 28 -day-old weaned pigs (Duroc × Landrace ×Yorkshire) with negative PCV2 antibody and initial body weight of (6.93±0.721) kg were allocated into 6 treatments with 9 replicates per treatment and 1 pig per replicate. On day 1 of the experiment, all pigs were inoculated with PCV2, and the basal diet was corn-soybean meal diet, and biotin was added to the basal diet at rates of 0, 0.10, 0.20, 0.30, 0.40 and 0.50 mg/kg diet, respectively. The experiment lasted for 35 days. The results showed that average daily gain (ADG) and  F/G of 35 days were significantly improved with 050 mg/kg biotin addition compared with those with 0 mg/kg (P<0.05); adding 0.30～0.50 mg/kg biotin significantly increased the serum IgG concentration (P<0.05) compared with that of 0~0.20 mg/kg; serum IFN-γ level in 0.30 mg/kg biotin group was higher in the later period of experiment than that of other groups; with biotin additive levels increasing, the ADG and F/G of 35  days and IgG concentration on day 21 and day 35 after inoculation showed quadratic or cubic curve regression. In conclusion, supplementation of 0.30～0.50 mg/kg biotin could significantly improve the serum IgG,IFN-γ concentration and the growth performance in the piglets challenged with PCV2.