Objective To summarize clinical features and changes of peripheral blood lymphocyte subsets in children with EBV-associated hemophagocytic syndrome. Methods Twenty children diagnosed with EBV-AHS were characterized by hemophagocytic syndrome and had the evidence of EBV infection.Clinical characteristics were analyzed and proportions of lymphocyte subsets of CD4+ ,CD8+, CD19+,CD16+CD56+ and CD4+/CD8+ in peripheral venous blood were determined by flow cytometry. Twenty healthy children matched in age and gender with these patients were selected as control. Results In all the diagnostic items of EBV-AHS, fever, decline of cells over two lineages in blood routine, enhanced lactate dehydrogenase ( ＞1 000 U/L) and ferritin ( ＞ 1 500 g/L),decreased high-density lipoprotein occurred in all the patients with an incidence of 100%. The percentages of CD8 + T and CD19 + B in children with EBV-AHS were higher than those in control group(53.70% ± 10.6% vs 27.05% ±8.22%,24.95% ±5.34% vs 11.85 % ± 4. 53 %, respectively), while levels of CD4 + T and CD16 + CD56 + NK cell were lower compared with control group (23.60% ±6. 42% vs 45.20% ±5.74% ,5.55% ±2. 87% vs 14. 70% ±4. 16% ,respectively ,P ＜ 0.01 ). Conclusion Disorder of cellular and humoral immunity happens in patients with EBV-AHS, which could be implicated in the pathogenesis and progression of EBV-AHS.