Abstract: This study aimed to investigate the influence of Glycyl-glutamine on the development of immune functions of Yuehuang chicken, and to investigate its effect on proliferation and secretion of chicken lymphocytes. In experiment one ,360 1-day-old Yuehuang chicken were randomly divided into 4 groups, with 90 birds in each group. Group 1 served as control, while group 2 to 4 were respectively supplemented ad libitum with 100,500 and 1 000 μg/L Gly-Gln via drinking water. On 45 and 80 days of age, 18 birds in each group were slaughtered and the bursa of Fabricius , spleen and thymus were weighted and blood samples were collected. At the same times, 3 birds in each group were selected and lymphocytes from blood and spleen were collected for measuring proliferation and secretion of IL-2 and IL-6. Experiment two was conducted to test the proliferation and secretion of lymphocytes when cultured with the addition of Gly-Gln. Lymphocytes from blood and spleen were isolated from 8week-old chicken without treatment of Gly-Gln, and culture in media added with 0, 0.6,1.2 and 2.4 mmol/L Glycyl-glutamine solution respertively. The results showed : (1) Supplementation of Gly-Gln had no significant effect on the development of Fabricius Bursa; but Gly-Gln significantly decreased the thymus indices at 1 000 μg/L level and improved the spleen indices at 500 μg/L level in 80-day-old chickens. (2) The additions of both 500 μg/L and 1 000 μg/L GlyGln significantly increased concentrations of IL-2 and IL-6 in the sera of Yuehuang chicken on 45 and 80 days of age, and enhanced blood lymphocyte proliferation , but inhibited spleen lymphocyte proliferation in 45-day-old chicken.(3) The addition of Gly-Gln at concentration of 2.4 mmol/L in the culture medium significantly enhanced lymphocyte proliferation ,but Gly-Gln did not affect the secretion of IL-2 and IL-6 form cultured lymphocytes.