Abstract: The effects of cysteamine on GH, SS and IGF-1 in the serum of Tibetan Sheep weaned lamb were studied. 40 80-day-old weaned lambs of Tibetan Sheep with the average initial weight of 16 kg（half male and half female） were randomly divided into 2 groups. 300 mg/（kg·BW） of CS was added in the concentrate of diet every two days. The trial lasted 42 days. The blood samples were collected from empty stomach of sheep by jugular vein in the morning of the 0th, 7th, 14th, 21st, 28th and 35th day after medication. The content of GH, SS and IGF-1 in the plasma was determined by radioimmunoassay. The results showed that adding CS in the concentrate in the test group could increase the content of GH and IGF-1 in the serum of weaned lambs of Tibetan Sheep to different extent and there was significant difference between test group and control group（P〈0.05）. SS decreased to different extent and SS content in test group had significant difference with that in control group from the 3rd week to the 42nd day.