Objective To detect the phenotypic conversion of tumor-associated macrophages (TAMs) through analyzing the expression levels of the polarization-related genes. Methods We identified the spontaneous breast cancer mice by genotyping and characterized them into the early stage and the advanced stage groups according to their tumor size. Single cell suspension of the tumor tissues were obtained by mechanical methods and TAMs of different stages were sorted by flow cytometry. We measured the mRNA levels of M1 macrophages-related genes IL-1β, IL-27, IL-6, CD80, CD86 and M2 macrophages-related genes arginase 1 (Arg1), IL-10, interleukin 4 receptor α (IL-4Rα), macrophage mannose receptor 1 (Mrc1), chitinase-like 3 (Chil3/Ym1) by real-time quantitative PCR in order to analyze the phenotypic conversion of TAMs during the tumor progression. Results In the early stage, TAMs expressed high levels of M1-related genes, such as IL-1β, CD80, CD86. On the contrary, TAMs of advanced stage expressed high levels of M2-related genes, including Arg1, IL-10, IL-4Rα as well as IL-6. Conclusion Phenotypic conversion of TAMs is present in tumor progression, and targeting the phenotypes of TAMs may provide potential therapies for breast cancer.