Immune microenvironment is closely related to the treatment and prognosis of tumors. Tumor-infiltrating immune cells exhibit significant heterogeneity in different stages of tumors. Single-cell RNA sequencing （scRNA-seq） is widely used in the study of various tumor microenvironment to analyze the biological behavior， mechanisms， and relationship between cells and the body at the single-cell level. The results showed that using scRNA-seq can deeply understand the immune characteristics of tumor-infiltrating immune cells.