Abstract: The effects of cysteamine on the weight gain and feed conversion efficiency of weaned lambs of Tibetan Sheep were studied. 40 80-day-old weaned lambs of Tibetan Sheep with the initial weight of （16.00＆#177;0.31） kg were randomly divided into 2 groups （test group and control group）. 300 mg/（kg＆#183;BW） of Cs was added in the diet concentrate every two days. The test period lasted for 42 days. The weight gain after drug administration 0, 7, 14, 21, 28 and 35 days was measured, and the weight of concrete in two groups was recorded. The results showed that 35 d weight gain of the weaned lambs of Tibetan Sheep in the test group of adding Cs in the concrete was enhanced by 43.25%（P〈0.01）. There was no significant difference during the first 7 days after drug administration and the difference was the most significant during 8~35 d. And then the promoting effects on the growth were gradually reduced with the prolonging of time and the concentrate-gain ratio decreased to 43.33%.