The aim of this study was evaluated the prevalence of Treg cells in peripheral blood in patients with gastriccancer, and investigate the effect of gastric cancer cells on their differentiation. ELISA was employed to assessthe concentrations of TGF-β and IL-10 in gastric cancer patients’ serum. Then, mouse gastric cancer cells wereco-cultured with T lymphocytes or T lymphocytes + anti-TGF-β. Flow cytometric analysis and RT-PCR werethen performed to detect Treg cells and TGF-β and IL-10 expression in gastric cancer cells. Our data showedthat the expression of TGF-β and IL-10 in the patients with gastric cancer was increased compared to the casewith healthy donors. The population of Treg cells and the expression levels of TGF-β and IL-10 in the co-culturegroup were much higher than in the control group (18.6% vs 9.5%) (P<0.05). Moreover, the population of Tregcells and the expression levels of TGF-β and IL-10 in the co-culture systerm were clearly decreased after additionof anti-TGF-β (7.7% vs 19.6%) (P<0.01). In conclusion, gastric cancer cells may induce Treg cell differentiationthrough TGF-β, and further promote immunosuppression.