This experiment was conducted to study the effects of Bacillus subtilis-dahlin synbiotics on growth performance and humoral immunity in weaner piglets. Seventy-two 21-day-old weaner piglets (Duroc × Landrace × Yorkshire) with an average body weight of (4.25±0.71) kg were randomly allocated into 4 groups with 3 replicates in each group and 6 piglets in each replicate. Piglets in the four groups were gavaged with the following solutions: nutrient medium (CG), nutrient medium+3.5 mg/mL dahlin (DG), nutrient medium+1.25×10⁸ CFU/mL Bacillus subtilis (BG), nutrient medium+3.5 mg/mL dahlin+1.25×10⁸ CFU/mL Bacillus subtilis (DBG), respectively. The gavage dose was 16 mL/d. The duration of the experiment was 14 d. The results showed as follows: 1) the average daily gain of BG and DBG was significantly higher than that of CG and DG (P<0.05). Simultaneously, the feed/gain and diarrhea rate of BG and DBG were significantly decreased compared with CG and DG (P<0.05). 2) The serum IgG content of DG, BG and DBG was significantly higher than that of CG (P<0.05), and compared with DG and BG, the serum IgG content of DBG was significantly increased (P<0.05). The serum IgA content of BG and DBG was significantly higher than that of CG and DG (P<0.05), meanwhile, the contents of C3 and C4 of DBG were significantly higher than those of CG (P<0.05). In conclusion, the Bacillus subtilis-dahlin synbiotics enhance the growth performance and humoral immune functions in weaner piglets.