Abstract: The effects of cysteamine（Cs） on the birth weight and weaning weight of Tibetan Sheep lamb were studied. 20 pregnant ewes with the age of （125±5）d were randomly divided into 2 groups （test group and control group）. 300 mg/（kg·BW） of Cs was added in the diet concentrate in test group every two days. The test period lasted for 90 days. The birth weight was measured after parturitionand two-month-old lambs was weaned and weighted. The results showed that adding Cs in the diet concentrate in test group could enhance the birth weight by 8.33%and the weaning weight of 2-month-old was increased by 13.73%.