This study was aimed to investigate the relationship between CD4(+)CD25(+) regulatory T cells, IL-2, TGF-beta and acute graft-versus host disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The percentage of peripheral blood CD4(+)CD25(+) Treg cells in CD4(+) T cells of 13 patients with hematological malignancies after allo-HSCT were detected by flow cytometry; serum levels IL-2 and TGF-beta in these patients were measured by ELISA. The results indicated that all the patients achieved engraftment. 5 patients developed aGVHD of grade I-II, 4 patients developed aGVHD of grade III-IV. The percentage of peripheral blood CD4(+)CD25(+) Treg cells out of CD4(+) T cells in patients without aGVHD was higher than that in patients with aGVHD (p < 0.05); the serum level of IL-2 in patients without aGVHD was lower than that of patients with aGVHD (p < 0.05); the serum level of TGF-beta in patients without aGVHD was higher than that of patients with aGVHD (p < 0.05). It is concluded that CD4(+)CD25(+) Treg cell level and the serum level of IL-2 and TGF-beta all are related to incidence and severity of aGVHD. These factors may be used as indicators for early evaluating and monitoring aGVHD after allo-HSCT.