Abstract: The experiment was conducted with the objective of examining the effects of high copper on the bursa of Fabricius in the chicken by the methods of experimental pathology and flow cytometry (FCM). 420 one-day-old Avian chickens were randomly divided into seven groups, and fed on control diet （Cu 11 mg/kg） and high copper diets （Cu 100 mg/kg,high copper group Ⅰ；Cu 200 mg/kg,high copper group Ⅱ；Cu 300 mg/kg,high copper group Ⅲ；Cu 400 mg/kg,high copper group Ⅳ；Cu 500 mg/kg, high copper group Ⅴ；Cu 600 mg/kg, high copper group Ⅵ）for six weeks,respectively. The results showed that histological changes were observed in high copper groups Ⅲ，Ⅳ，Ⅴand Ⅵ in comparison with those of control group. The weight and the growth index of the bursa of Fabricius were higher in high copper groupsⅠand Ⅱ（P＞0.05）,and lower in high copper groups Ⅲ，Ⅳ，Ⅴand Ⅵ than that in control group（P＜0.05 or P＜0.01）. The proliferation index（PI） of the bursa of Fabricius was increased in high copper groups Ⅰand Ⅱ（P＞0.05）,and decreased in high copper groups Ⅲ，Ⅳ，Ⅴand Ⅵ（P＜0.05 or P＜0.01）compared with that of control group. Percentage of apoptotic lymphocytes in the bursa of Fabricius was higher in high copper groups Ⅲ，Ⅳ，Ⅴand Ⅵ than that in control group（P＜0.05 or P＜0.01）.It is concluded that dietary copper in excess of 300 mg/kg inhibited the development of bursa of Fabricius，caused pathological changes in the bursa of Fabricius and impaired humoral immune function，and that 11200 mg/kg of copper in diet was helpful for the development of the bursa of Fabricius.