Monocyte chemoattractant protein-1(MCP-1) is released from the macrophages and endothelial cells, regulated luteotropic and luteolytic actions of macrophages and induced luteolysis. However, the mechanisms of MCP-1 on the development and maintenance of pregnant corpora lutea are thoroughly unknown. In this experiment, TUNEL stain, ED1, ED2, and MCP-1 immunohistochemistry on the corpora lutea of pregnant rats were carried out to reveal the role of macrophages in the developing corpora lutea. In the postpartum corpora lutea, the number of macrophages was increased significantly, and the intensity of ED1 and ED2 immunoreactivity in macrophages were increased moderately, and MCP-1 immunoreactivity was also increased. In conclusion, macrophages in the postpartum corpora lutea may exert phagocytic action mainly, and the macrophages in the pregnant corpora lutea maintain the structure and function of lutein cells.