Lymphocyte subset testing is used to assess the strength of immune function by detecting the counts of T-lymphocytes, B-lymphocytes, and NK-cells, which are important lymphocyte components that make up the body’s immune defense. Different cells have different functions, e.g. T lymphocytes include Th1 and Th2 cells, as well as CD4-positive T cells and CD8-positive T cells; B cell system produces antibodies, and NK cells are the body’s natural killer cells; different lymphocyte subpopulations will play a role in the body’s immune status and immune defense function from different angles. For some infectious diseases and non-infectious diseases, especially hematologic tumors, lymphocyte subpopulation monitoring is often needed to determine the body’s defense function against the outside world. At the same time, lymphocyte subpopulation monitoring is often needed for hematologic diseases, because different hematologic diseases often have different types of blood cell proliferation, and monitoring helps to detect abnormal lymphocyte classification, which is an important guide for the diagnosis of hematologic diseases.