In order to explore the effects of cysteamine and daidzein on gene expression of IGF-Ⅰ mRNA in the tissue of liver, muscle and skin in Northeast fine-wool sheep. Twenty-one healthy Northeast fine-wool sheep with body weight of 27～28 kg and age of 5～6-month-old were randomly divided into 7 groups with 3 replicates and each replicate had 1 sheep. Using real-time fluorescence quantitative PCR detected the IGF-Ⅰ mRNA expression on liver, muscle and skin. The results showed as follows: 1) both cysteamine and daidzein could significantly enhance the growth performance of Northeast fine-wool sheep (P<0.05), and the 7.5 mg/kg BW cysteamine group and 7.5 mg/kg BW cysteamine＋3 mg/kg BW daidzein group had the better effects; 2) cysteamine and daidzein could evidently increased the expression of gene IGF-Ⅰ in the liver and muscle of Northeast fine-wool sheep (P<0.05), but no significant difference was found among trial groups (P>0.05); 3) compared with the control group, the IGF-Ⅰ mRNA expression on the skin in 3 mg/kg BW daidzein group, 6 mg/kg BW daidzein group and 7.5 mg/kg BW cysteamine＋3 mg/kg BW daidzein group were significantly improved (P<0.05), but no significant difference was found among the control group, 7.5 mg/kg BW cysteamine group, 15 mg/kg BW cysteamine group and 15 mg/kg BW cysteamine＋6 mg/kg BW daidzein group (P>0.05). It was concluded that cysteamine and daidzein could improve the IGF-Ⅰ mRNA expression in liver and muscles, but cooperation application did not make the gene IGF-Ⅰ mRNA expression obviously improved in the liver, muscle and skin tissue. In summary, adding 3 mg/kg BW of daidzein had the best effect.［Chinese Journal of Animal Nutrition, 2009，21(6):967-973］