To investigate the clinical effect of levonorgestrel intrauterine sustained-release system (NG-IUS)for treating patients with endometrial hyperplasia and without atypical hyperplasia, and to find effective evaluation indexes in the treatment process, so as to provide evidences for reducing the occurrence of endometrial malignant tumors. Methods: The clinical data of 219 patients with endometrial hyperplasia and without atypical hyperplasia treated with LNG-IUS from October 2018 to March 2020 were analyzed retrospectively. The correlation between the endometrial reversal of the patients and their age, menstrual pattern, treatment time, endometrial thickness after treatment, and so on were statistically analyzed. Results: Among the patients with endometrial hyperplasia and without atypical hyperplasia, the patients with aged in <40 years old accounted for 12.3%, with aged in 40-50 years old accounted for 67.6%, and with aged in ≥50 years old accounted for 20.1%. The endometrial reversal rate of the patients treated within 1 year was 90.5% (133/147), and that of the patients treated  ≥1 year was 96.4% (211/219), which had significantly different (P＜0.05). The endometrial reversal rate of the patients with abnormal menstrual pattern after 1 year of treatment was 34.1% (72/211), and that of the patients with normal menstrual pattern after 1 year of treatment was 65.9% (139/211), which had significantly different (P＜0.05). In the patients without reversive endometrium after 1 year of treatment, there were 6 patients with endometrial thickness <7mm and 2 patients with endometrial thickness ≥7mm, which had no significant different (P＞0.05). Conclusion: The rate of endometrial hyperplasia of the patients with endometrial hyperplasia and without atypical hyperplasia after LNG-IUS treatment is high, and which increases with prolong of LNG-IUS inserted. The patients with abnormal menstrual pattern has lower rate of endometrial reversion. The endometrial thickness of the patients measured by ultrasound cannot be used as a judgment index of their unreversive endometrium.