Objective: To analyze the changes and significance of CD4⁺T lymphocyte subsets and lymphocyte subsets in peripheral blood of 96 children with hemophagocytic syndrome (HPS). Methods: A total of 96 children with HPS who were admitted to the department of hematology and oncology of the hospital from February 2010 to January 2017 were selected as the subjects (HPS group). They were treated with chemotherapy after admission according to the relevant recommended regimen. According to the therapeutic effect, the children were divided into a good prognosis group and a poor prognosis group; 40 healthy children admitted to the hospital at the same time were selected as a control group. The fasting venous blood of children with HPS was collected at the 2nd day after the admission and after the end of treatment, while the fasting venous blood of the control group was collected in the morning on the day of physical examination. The peripheral blood CD4⁺T cell subsets Th1, Th2, Th17 and Treg, lymphocyte subsets CD3⁺, CD4⁺, CD8⁺and CD19⁺ were determined by flow cytometry. Results: The Th2, Th17 and Th17/Treg, CD3⁺ and CD8⁺ were significantly higher, while Th1/Th2 and Treg, CD4⁺ and CD4+/CD8⁺ were significantly lower in HPS group than in the control group (P<0.05), there was no significant difference in CD19+ between the two groups (P>0.05). After three stages of chemotherapy, 26 cases (27.08%) were effectively treated, 36 cases (37.50%) were relieved, 7 cases (7.29%) had disease activity, 3 cases (3.13%) had recurrence, and 24 cases (25.00%) died. The Th2, Th17 and Th17/Treg, CD3⁺ and CD8⁺ were significantly higher, while Th1/Th2 and Treg, CD4⁺ and CD4⁺/CD8⁺ were significantly lower in the poor prognosis group than in the good prognosis group (P<0.05), there was no significant difference in CD19⁺ between the two groups (P>0.05). Conclusion: Children with HPS have abnormal CD4⁺T cells subsets and T cell subsets in peripheral blood, which can be used to evaluate the damage of immune function and prognosis in children.