Objective To study the effects of adenosine 2A receptor activation on activation, proliferation, and toxicity of T lymphocytes stimulated by phytohemagglutinin (PHA) in vitro. Methods A model of activated T cells was established by stimulating the cells with PHA. Those T cells were treated with different concentrations of adenosine 2A receptors agonist (0.01 μmol/L, 0.1 μmol/L, 1 μmol/L, and 10 μmol/L CGS21680). The expressions of CD69, CD25 and proliferation of T cells were measured by fluorescent antibody stain and flow cytometry. ELISA method was used to detect IL-2 and INF-γ levels. Results All concentrations of CGS21680 significantly inhibited the expressions of CD25 and CD69 on PHA-stimulated T cells surface and proliferation of T cells （Plt;0.05， Plt;0.01）. IL-2 and INF-γ secreted by T cells were significantly suppressed, too （Plt;0.01）. Conclusion Activation of adenosine 2A receptor can effectively inhibit the activation, proliferation, and toxicity of T cells in vitro.