Objective To detect the changes of T lymphocyte subset levels in peripheral blood of acute myeloid leukemia (AML) patients and explore the clinical significance. Methods Total of 68 newly diagnosed AML patients and 76 healthy candidates (healthy controls) were selected for the study. Prognostic risk stratification of AML patients was stratified according to Chinese guidelines for diagnosis and treatment of adult AML (not acute promyelocytic leukemia) (2017). The enrolled patients were divided into high-risk group (20 cases) and non-high-risk group (48 cases). The curative effect of AML patients was evaluated after standard chemotherapy. The flow cytometry technique was used to detect T lymphocyte subset levels in peripheral blood of the AML patients and the healthy controls. Results Proportions of CD3⁺, CD4⁺ T cells as well as CD4⁺/CD8⁺ ratio in AML group were significantly lower than those in healthy controls (all P<0.05), but the proportion of regulatory T (Treg) cells was significantly higher than that in healthy controls (P<0.05). The proportions of CD3⁺, CD4⁺ T cells and CD4⁺/CD8⁺ ratio in high-risk patients were significantly lower than those in non-high-risk patients (all P<0.05). The proportion of Treg cells in high-risk patients was significantly higher than that in non-high-risk patients (P<0.05). The proportions of CD3⁺, CD4⁺ T cells and CD4⁺/CD8⁺ ratio in patients who achieved complete remission (CR) (n=41) were significantly higher than those in patients without CR (n=27) (all P<0.05). However, the proportion of Treg cells in AML-CR patients was significantly lower than that in patients without CR (P<0.05). Conclusion Observation of T lymphocyte subsets and CD4⁺/CD8⁺ ratio can benefit to disease monitoring of patients with AML.