Abstract: The experiment was conducted to study the effects of high zinc on immune function in chicken. 200 one-day-old Avian broilers were randomly divided into four groups and fed on diets as follow: basic diet (Zn 100 mg/kg, control ［Ⅰ］) and high zinc diets (Zn 1 500 mg/kg ［Ⅱ］, 2 000 mg/kg ［Ⅲ］, 2 500 mg/kg ［Ⅳ］) for seven weeks. The chicken in groups Ⅱ, Ⅲ and IV grew very slowly. At the same time， lymphocytes of the thymus, bursa of Fabricius and spleen were significantly depleted, degenerated and necrotic histopathologically. The weight and growth index of lymphoid organs，proliferating index of lymphocytes， the ANAE⁺ ratio of peripheral blood lymphocytes and erythrocyte C₃bRR ratio markedly decreased and ICR ratio increased markedly in high zinc groups when compared with control group. The above mentioned results indicated that proliferations of lymphocytes were impaired by high zinc.