Objective:To compare the features of decidual monocyte-macrophages separated from placental tissues with different gestational ages and explore the role of these immunocytes in immunological tolerance to fetal antigen and the activation of parturition. Methods:We separated decidual cells from healthy decidua samples mechanically,which were obtained after selective abortions at 16 to 25 weeks,or after term deliveries(spontaneous term vaginal deliveries).After purified by MACS,macrophages were analyzed by flow cytometry for molecular makers on cellular surface and cytokines secretion. Their abilities of inducing proliferation were also identified by CCK-8 incorporation assay. Besides,cytokines levels of the cultured allogenic T cells mixed with macrophages were detected. Results:CD14+ macrophages with a purity of 93.32% were obtained. Decidual macrophages origined from normal term-placental tissues expressed low levels of CD80,CD86 and HLA-DR,with no expression of CD83,and secreted low levels of IL-10 and TGF-β. They slightly stimulated allogenic T cells to proliferate and produce low IL-10 and high TGF-β. In contrast,we found higher levels of CD80,CD86,HLA-DR and CD83 expressed on macrophages from mid-pregnancy placenta with higher levels of IL-10 and TGF-β. They slightly stimulated allogenic T cells to proliferate and produce higher IL-10. Conclusion:Monocyte-macrophages separated from placental tissues with different gestational ages are different in biological characteristics. Our results suggests IL-10 may be related to the function of decidual macrophages at mid-pregnancy.