Objective To analysis the T lymphocyte subsets distribution of patients with myelodysplastic syndrome (MDS)-RA and-RCMD,assess the immune status of MDS patients,and analysis the effects of cyclosporine on T lymphocyte subsets.Methods Using flow cytometry (FCM) on MDS-RA and -RCMD patients and 13 normal controls peripheral blood samples for T lymphocyte subsets,detection of patients with RA and RCMD lymphocyte subsets before and after 6 months of treatment in the application of cyclosporine-based immunosuppressive regimen.Results The MDS group Th cells (CD; CD;),Th/Ts ratio were lower than those in normal control group (t =13.39,3.64,all P ＜ 0.05).Ts cells (CD3+ CD8+) express higher than that in normal control group [(29.07±3.88) ％ vs (21.80±3.63) ％] (t =6.47,P ＜ 0.05).Before and after treatment of Th cells,Th / Ts ratio,Ts cells of T lymphocyte subset were significant difference [(35.72±5.02) ％,(29.07±3.88) ％,(1.89±0.51) ％ vs (38.19±4.98) ％,(26.03±3.03) ％,(1.96±0.35)％] (t =0.39,2.65,3.57,all P ＜ 0.05).Cyclosporine treatment after 6 months of effective and ineffective group of T cell subsets,Th cells (CD3+ CD4+),Th/Ts ratio of T lymphocyte subsets,there was significant difference in Ts cells [(42.79±7.74) ％ vs (36.46±.1.28) ％,(22.14±.3.91) ％ vs (27.51±2.84) ％,(2.40±0.40) ％ vs (2.08±0.11) ％](t =67.65,3.77,3.57,all P ＜ 0.05).Conclusion MDS patients with T-lymphocyte subsets immune disorders lead to immune dysfunction,cyclosporine may improve the imbalance of T lymphocyte subsets of MDS patients.