Abstract: Macrophages affected by different simulating factors can be differentiated into M1-type macrophages with anti-tumor activity and M2-type macrophages with tumor-promoting activity. Main macrophages in tumor tissue are M2-type and they are involved in the process of tumor genesis, development, invasion and metastasis. Specific stimulation can re-differentiate M2-type macrophages into M1-type, thereby to inhibit tumor growth. This article briefly reviews the differentiation of tumor-associated macrophage and its close relationship with tumor.