Abstract: [ Objective ] The aim of the present study was to investigate the differences in MSTN gene expression in different tissues of Tan sheep with different ages. [Methods] According to the published MSTN gene sequence of sheep （NM_001009428.1） in GenBank, a pair of specific primers was designed to amplify the part of cDNA sequence of MSTN using RT-PCR technique. The relative expression level of MSTN gene in longissimus dorsi, leg muscle and breast muscle of Tan sheep with different ages were analyzed by Real-time PCR. [ Results ] The results showed that the highest expression of MSTN gene were found in longissimus dorsi, followed by breast muscle and leg muscle; with the increase of age of month, the expression of MSTN gene in three kinds of muscle tissues showed a tendency that firstly increased, then decreased and eventually increased. [Conclusions] There were differences of MSTN mRNA expression in muscle tissues of Tan sheep with different ages, which might impact on their growth and development as well as meat production performance.