Abstract: Objective To explore the effect of low-dose decitabine (DAC) on the proliferation and anti-tumor ability of CD4-positive T cells. Methods CD4-positive T cells were separated from human peripheral blood mononuclear lymphocytes by magnetic beads,and DAC was added during the culture in vitro.The dose and time of adding DAC were determined by cell proliferation assay,and then the memory phenotype of DAC modified CD4-positive T cells were detected by flow cytometry.Finally,the anti-tumor activity and cytokine secretion ability of DAC modified CD4-positive T cells were verified by cell killing test in vitro. Results Compared with the control group,low-dose DAC modified CD4-positive T cells had significantly enhanced cell proliferation ability (P<0.05),higher memory phenotype CD62L expression (P<0.05),and increased cytotoxicity and cytokine secretion ability in vitro (P<0.05,respectively). Conclusion The proliferation and long-term tumor inhibition ability of CD4-positive T cells modified by low-dose decitabine are enhanced.