Abstract: Four sheep installed chronic catheters in the portal vein,hepatic vein and mesenteric vein were used to study the effects of clenbuterol on metabolic hormones.The results are:1)The GH level of portal vein is markedly increased during clenbuterol treatment period (0.8 mg/kg BW,twice daily for five days);2)The GH level of hepatic vein with clenbuterol-treated is similar to that of control;3)The IGF-Ⅰ concentration of hepatic vein is markedly elevated and IGF-Ⅰ of portal vein is maintained a higher level in clenbuterol treatment period.4)The insulin concentration of hepatic blood is decreased with clenbuterol-treated.These showed that the changes of those hormone levels in clenbuterol treatment played an important role in regulation of growth and metabolism in sheep.