It is essential for progesterone to inhibit estrogen-induced proliferation of endometrial epithelial cells (EECs) and make endometrial epithelium to convert into the secretory epithelium for the preparation of embryo implatation. But the mechanism of progesterone effect on EECs remains unclear. Recent studies have indicated that some reproductive hormones can regulate the expression of some special genes in post-transcriptional level. MicroRNAs are important post-transcriptional regulators in target mRNA, thus they are involved in many physiological and pathological processes. We speculate that there should be progesterone-induced microRNAs which mediate the physiological effect of progesterone on EECs. In this study, 20 six-week-old ovariectomized female Kunming mice were randomly divided into 2 groups, 10 mice for each. One group (P4 group) was treated both estrogen (100ng / daily for 2 days) and progenstrone(2 mg). The other one (control group) was treated with only estrogen and sesame oil. All mice were sacrificed and their uteri were collected. The EECs were enzymatically isolated and the total RNA was respectively extracted from each group. Small RNA molecules were purified by PAGE, ligated a pair of Solexa adaptors and amplified by PCR, thus 90 bp of DNA were isolated with agarose gel. The purified DNA was used for cluster generation and sequencing analysis using the Illumina’s Solexa Sequencer. Then we evaluated sequencing quality, calculated length distribution of small RNA reads and filtrated impure reads. Finally, clean reads were identified and analyzed based on the known mice miRNA of miRBase database 19. The miRNA expression of two groups was compared to find out the differentially expressed miRNA. The results showed that there were 149 up-regulated miRNAs of which the differences is more than twice of control group. Afterwards, the target genes of these miRNAs were predicted using the following algorithms: miRanda, PicTar, and TargetScan. 22 miRNAs were selected from the 149 up-regulated miRNAs, of which the target gene proteins are involved in significant biological functions, such as cell adhesion, transmembrane transport, cell cycle and metabolism (table). To data, 9 microRNAs (miR-23a-3p, mmu-miR-26a-5p, mmu-miR-1a-3p, mmu-miR-133a-3p, mmu-miR-195a-5p, mmu-miR-3473b, mmu-miR-204-5p, mmu-miR-145a-5p, mmu-miR-143-3p) have been verified by real time PCR. The results proved that their expression is progesterone-dependent on the EECs. In our conclusion, progesterone can specifically regulate the expression of some miRNAs in EECs, which possibly mediate the effect of progesterone on the structure and function of endometrial epithelium for preparing for implantation through influencing some functinal proteins. This project will be helpful for further exploring the molecular mechanism of progesterone’s effect on EECs.