Abstract: Chronic myelomonocytic leukemia (CMML) is a rare heterogeneous hematological malignancy characterized by persistent monocytosis, which is crucial for distinguishing it from other diseases, especially reactive mononucleosis. With the development of testing technology and the increase in understanding of human monocyte subpopulations, some new identification methods are widely used, including selecting specific surface markers, typing monocyte subsets, and so on. However, the method of selecting specific surface markers by flow cytometry for the diagnosis of chronic myelomonocytic leukemia has problems of low sensitivity and poor specificity. Up to now, no completely qualified surface markers have been found. Some researchers proposed to quantify monocyte subsets by CD14/CD16 typing. The diagnosis of chronic myelomonocytic leukemia by the proportion of monocyte subsets has been supported by many studies. However, some scholars still question the accuracy of this method in diagnosis, and this article provides a literature review on this issue.