Objective To investigate the changes of T cell subsets including Th1,Th2,Th17 and Treg in the hand,foot and mouth disease(HFMD) patients.Methods 35 EV71 induced HMFD patients and 12 non-infectious children were included in this study.Patients were divided into mild symptoms group and severe symptoms group.The ratios of Th1,Th2,Th17 and Treg were analyzed by flow cytometry.Results Sixteen mild cases and 19 severe cases were included in the 35 patients.No statistical difference of children′s age and sex were found among the groups(P>0.05).The proportion[M(P25,P75)] of Th1 cells of mild and severe groups were 10.65%(8.73%,14.08%) and 15.51% (13.47%,18.31%),respectively,which were significantly higher than normal control group 5.51% (3.61%,8.61%)(P<0.05).The proportion of Th2 cells of mild and severe groups were 4.32%(2.60%,5.32%) and 3.87% (2.34%,5.32%),no significant difference from control group 2.11% (1.02%,5.11%)(P<0.05).The proportion of Th17 cells of mild and severe groups were 8.32%(5.25%,12.33%),7.36% (5.05%,11.9%),significantly higher than that of normal control group 4.23% (2.44%,6.22%)(P<0.05).The proportion of Treg cells of mild and severe groups were 1.46% (0.31%,2.73%),1.59%(0.35%,2.62%),no significant difference from the control group 1.78% (0.31%,2.77%)(P<0.05).Conclusion The Th1/Th2 and Th17/Treg ratios of HFMD patients with EV71 virus infection were changed,and the Th1 and Th17 cells may play an important role in the in the disease and body′s resistance.