The effects of dietary supplementation with Clostridium butyricum on growth performance and humoral immune response in Miichthys miiuy were evaluated. One hundred and fifty Miichthys miiuy weighing approximately 200～260 g were divided into five groups and reared in 15 tanks with closed circuiting culture system. The animals were fed 5 diets: basal diet only (control) or supplemented of the basal diet with C. butyricum at doses of 103 (CB1), l05 (CB2), 107 (CB3) or 109 (CB4) CFU/g.Compared with the control, the serum phenoloxidase activity was significantly increased by the supplementation (P＜0.05), acid phosphatases activity was increased significantly (P＜0.05) at the doses of 109 CFU/g. Serum lysozyme activity peaked at dose of 107 CFU/g and in the skin mucus at dose of 109 CFU/g. Immunoglobulin M level in the serum and skin mucus was increased except at dose of 103 CFU/g (P＜0.05). The growth at the dose of 109 CFU/g was higher than that of the control (P＜0.05). It is concluded that supplementation ofC. butyricum can mediate the humoral immune responses and improve the growth performance in Miichthys miiuy.