Abstract: 400 AA broilers of 1 day were allocated into 4 treatments, 5 replicates per treatment, 20 broilers per replicate. The basal diet was wheatcasein diet. Biotin was added in the basal diet at 0.3 mg/kg, 0.9 mg/kg and 2.7 mg/kg. There were 4 diets including the control of basal diet. The results showed as follows: (1) Addition of biotin enhanced their development and elevated their weight index. The antibody titer to Newcastle and IgG content were elevated by addition of biotin. The antibody titer to Newcastle of 0.9 mg/kg and 2.7 mg/kg treatments were higher significantly than that of the control and 0.3 mg/kg treatment (P<0.05). The IgG level of 2.7 mg/kg treatment was higher markedly than that of the control (P<0.05). (2) Addition of biotin enhanced significantly B-lymphocyte transformation ratio in blood (P<0.05), and Tlymphocyte and Blymphocyte (P<0.05) transformation ratio in spleen. In spleen, the cell content of expressing CD3⁺ , CD4⁺ and CD8⁺ were reduced significantly by addition of biotin (P<0.05). The cell content of expressing CD3+, CD4⁺ and CD8⁺ of 2.7 mg/kg treatment was lower markedly than that of the control and 0.3 mg/kg treatment (P<0.05). In blood, addition of biotin reduced significantly the cell content of expressing CD3⁺ (P<0.05). The cell content of expressing CD3⁺ of 2.7 mg/kg treatment was lower markedly than that of the control and 0.3 mg/kg treatment (P<0.05). (3) Biotin addition elevated serum T3, T4, growth hormone and cortisol (P>0.05), and what’s more, no noted difference existed among the biotin addition treatments (P>0.05).