Tumor metastasis is the basic feature and important sign of malignant tumors,and the main cause of death for most cancer patients.The tumor microenvironment is closely related to tumor metastasis and a deep understanding of the relationship between tumor microenvironment and tumor metastasis has positive guiding significance for the prevention and treatment of tumors.The occurrence,development and metastasis of tumors involve a series of complex biological processes.In the process of tumor metastasis,the tumor microenvironment cooperates with tumor cells.Tumor microenvironment is composed of cellular components,physical components and biochemical components,and it participates in important biological processes such as tumor growth,invasion,metastasis,neovascularization,immune escape,and tumor drug resistance.The study of tumor microenvironment can help us better understand the biological behavior of tumor and control the occurrence,development and metastasis of tumor.