Tropnin T (TnT) is the troponin complex subunit that most strongly binds to tropomyosin (Tm). Various TnT isoforms through alternative mRNA splicing are specifically expressed during development and/or in different muscle types, indicating that these forms have specialized functions in muscle contraction. The Tx structure has been identified in TnT isoforms specifically expressed in the breast of Galliformes and Craciformes. In the present study, monoclonal antibody 6B8 that recognizes Tx epitope was used to detect the expression of Tx-TnT isoforms during the different developmental stages of breast and leg muscles between Hongshan chicken and Avian broiler. The results confirmed that the Tx epitope is only present in the breast but not leg muscles of both chickens. The least square analysis showed the quantum of Tx-TnT expressed in the breast muscles increased during development and had significant difference (P < 0.05) between Hongshan chicken and Avian broiler. The correlations between the expression quantum of Tx-TnT and the breast muscle weight were 0.91236 for Hongshan chicken and 0.87624 for Avian broiler, respectively, and significant at 0.05 level.