Objective: To study the effect of levonorgestrel Intrauterine System on insulin-like growth factor-l (IGF-1) and the result of levonorgestrel Intrauterine System Prevention pelvic inflammatory disease. Methods: The 450 cases of hysteroscopic resection for endometrial polyps divided to study group(198 cases) who were placed levonorgestrel Intrauterine System in uterus after hysteroscopic electroresection, and control group(252 cases) who were not placted at random. The IGF-1 expression of endometrial biopsy specimens during intraoperative and rechected after 6 months were check out by immunohis to chemistry. Patients were followed up for 2Syears to analyse the effluence of pelvic inflammatory disease. Results: All patients had successful surgery. Intraoperative specimens compared with afteroperation specimens of the IGF-1 expression, there was a significant differencesSin study group but control group. Followed up for 2 years, 14 cases has pelvic inflammatory disease in study group,39 cases has pelvic inflammatory disease in control group,there was a significant differences. The thickness of endometrium after operation is lower than before operation in study group but control group. Conclusions:It may be the mainSmechanism of Prevention pelvic inflammatory disease and inhibition endometrium that Levonorgestrel intrauterine system can prevent endometrial IGF-1 expression.