Abstract：【Objective】To investigate the disturbance between Th17 and Treg cell balance in ovarian endometriosis patients. 【Methods】Case-control study comparing 40 women with histo-pathologically confirmed ovarian endometriosis and with 40 control infertility women without visible endometriosis foci，pelvic inflammations who were subjected to laparoscopic surgery during the same period. Peripheral blood，peritoneal fluid，ovarian ectopic endometrial tissue and eutopic endometrial tissue of ovarian endometriosis patients and controls were collected during surgery. T lymphocytes subpopulations in peripheral blood were analyzed by flow cytometry using specific monoclonal antibodies recognizing CD4+，CD25+ and CD127-markers and CD3+，CD8-and IL-17A+markers. Then， IL-17，IL-22，IL-10and TGF-β concentration in the serum and peritoneal fluid was determined using enzyme linked immunosorbent assay（ELISA）. Also，Q-PCR was performed to verify Foxp3 mRNA and ROR-γt mRNA expression differences in eutopic and ectopic endometrial tissue.【Results】1.The percentage of CD4+CD25+CD127-Treg cells was significantly decreased in the peripheral blood ofwomen with ovarian endometriosis compared with control women. On the other hand，the proportion of CD3+CD8-IL-17A+ Th17 cells was significantly increased in the peripheral blood of women with endometriosis compared with control women. 2. Comparing with the controls，the concentration of IL-17 and IL-22 was significantly higher in the serum of women with ovarian endometriosis，and the levels of IL-10 and TGF-β were significantly lower in the serum of women with endometriosis. On the contrast，in the peritoneal fluid of women with ovarian endometriosis，the concentration of IL-17 and IL-22 were lower，and the concentration of IL-10 and TGF-β were significantly higher than the controls. 3.Foxp3 mRNA expression level was significantly elevated in ectopic endometrial tissue of patients with ovarian endometriosis compared with eutopic endometrial tissue，while the ROR- γ t mRNA expression level of ectopic endometrial tissue was significantly decreased than eutopic endometrial tissue.【Conclusion】The present study verifies the imbalance of Th17/Treg in peripheral blood，peritoneal fluid and endometrial tissue in ovarian endometriosis patients，which implies the immune dysregulation and the disturbance of immunity homeostasis in the establishment and progression of endometriosis.