Objective:To observe the stimulating effect of C main Peptide purified from Mycobacterium tuberculosis peptide antigens(Mtb Ag) on human ??T cells, and the effect of C main peptide on the Mtb Ag activated ??T cells in vitro. Methods:C main peptide was used to stimulate fresh ??T cells of normal subjects in different doses for 10 d and the responded cells were phenotyped by flow cytometry. Furthermore,C main peptide was used to restimulate the activated ??T cells ,and then analyse the expression of early activation marker molecule CD69 in ??T cells by flow cytometry and the activity of proliferation of ??T cells by MTT assay. Results:C main peptide could stimulate the proliferation of fresh ??T cells predominantly, and it also could promote the expression of CD69 in activated ??T cells and enhance its activity of proliferation. Conclusion:C main peptide purified from Mtb Ag is a kind of specific stimulator of human ??T cell in vitro.