Objective To study the influence of progesterone on the number of the mouse uterine macrophages and the expression of its membrane receptors CD14 and CD204, and to explore the role of pro-gesterone and macrophage in uterus regional immunity. Methods 1. Twenty-five non-pregnant and healthy mice were randomly and evenly divided into blank control group, negative control group and experimental group which divided into low, medium and high progesterone concentration subgroups in advance and every group had 5 mice. The progesterone at the doses of 0.4mg, 2.0mg, and 4.0mg were intracutaneously injected into the mice of the experimental group, respectively, while the same doses of placebo were injected into the negative control group in the same condition and both were injected continuously for 5 days; the blank control group was stayed intact. 2.Gestational day 4 to 5 mice, the 15, were also divided into blank control, negative control and experiment groups randomly, 5 mice in each group. The progesterone at the dose of 4mg was intracutaneously injected into the experimental mice in the morning, and as well the same doses of placebo were injected into the negative control group mice; the blank control group was left intact. All of the above mice uteri were collected 6 hours later after the final injection. Non-specific esterase(α-NAE) staining and immunohistochemistry methods were used to identify the varieties of α-NAESUP>+/SUP> ,CD14SUP>+ /SUP>,CD204SUP>+/SUP>macrophages in the uterus. Results Compared with the negative control group, after injecting progesterone, the amount of the uterine macrophages with positive CD14 receptor immunohistochemical staining were significantly decreased with dose increasing in the non gestational group. For the gestational day 4 to day 5 mice, the amounts of the uterine macrophages with the positive CD14 and CD204 receptors immunohistochemical staining were significantly increased(EM>P/EM><0,01). Conclusion Progeterone can affect the regional immunity of uterus by adjusting the quantity of macrophages or its distribution or the expression of its membrane receptor. And the macrophages from alternative activation pathway might have a contribution to the maintenance of the maternofetal immune tolerance.