Abstract: Objective To explore the expression levels and significance of T cell subgroups in the peripheral blood of patients with primary Sj?gren′s syndrome (PSS).Methods Flow cytometer was applied to detect CD3 +,CD3 +CD4 +CD8 -,CD3 +CD4 -CD8 +,CD3 +CD4 -CD8 - and CD4 +CD25 +high expression levels in 32 PSS patients (observation group)and another 35 healthy people tak-ing physical examination (control group),which were then compared between groups.Results There were no significant differences between two groups in CD3 + and CD3 + CD4 - CD8 + expressions (P >0.05).The ratios of CD4 +/CD8 + and CD3 +CD4 +CD8 - subgroups increased evidently (P <0.01), while those of CD3 + CD4 - CD8 - double-negative T cells and CD4 + CD25 +high subgroup decreased markedly in observation group (P <0.01).Conclusion T cell subgroup expressions are abnormal in PSS patients,and over proliferation and infiltration of CD4 + cells is the risk factor of auto-immunologi-cal diseases,while the decrease of CD3 +CD4 -CD8 - double-negative T cells and CD4 +CD25 +high sub-group can lead to the damage of body immunological tolerance,which may be one of the important fac-tors for the development of PSS.