Objective:To analyze the effect of levonorgestrel releasing intrauterine system ( Mirena) on endometrium in the pa-tients with anovulatory uterine bleeding. Methods:Totally 67 cases of anovulatory uterine hemorrhage were treated with Mirena. The menstrual blood volume, uterine endometrial thickness, hemoglobin, endometrial ET content and complications were recorded before and after the treatment. Results:After the 12-month treatment, the menstrual blood volume and endometrial thickness were significant-ly decreased, and hemoglobin was significantly increased (P<0. 01). The percentage of abnormal uterine bleeding was significantly decreased, the ET content in endometrium was significantly decreased (P<0.05), and the ET content was decreased significantly with the prolongation of the treatment time. The complication rate was reduced from 50. 74% to 7. 46%. Conclusion:Mirena is nota-bly effective in the treatment of the patients with anovulatory uterine bleeding.