Abstract: In order to study the effects of cysteamine （CS） on the development of immune organs, 100 1-day-old local chickens were randomly divided into two groups, 50 chickens in each group. The chickens of control group were fed with basal diet, while that of experiment group with basal diet supplemented 0.1% CS. The test period was 30 d. At the end of the experiment, 20 chickens were randomly selected from each group and slaughtered by bloodletting in jugular vein. Then thymuses, bursae of Fabricius and spleens were collected and then fixed by Bouin liquid. Paraffin sections were prepared, stained with HE, observed under microscope （Olympus） and taken photographs. As shown by the results, the chickens in experiment group had following changes compared with the control group： the cortex of thymic lobule was thicker and lymphocytes gathered in cortex; the amount of thymic corpuscle decreased; the amount of lymphoid nodule in bursa of Fabricius increased, and lymphoid nodules were developing; the cortex of bursa of Fabricius incrassated and more lymphocytes appeared in clearly separated cortex and medulla, while the bursae of Fabricius atrophied and deteriorated in the control group; the structure of spleen was clear and amount of splenic nodule increased in white pulp. The results showed that CS supplemented to diet should promote the development of lymphic organ, and thus enhance immune functions of chickens.