To compare the contraceptive efficacies and side effects of Mirena (levonorgestrel-releasing intrauterine system, LNG-IUS) inserted immediately after artificial abortion and in the period of regular menstruation.A total of 166 female subjects volunteered for the insertion of LNG-IUS. They were divided into 2 groups. Eighty-six female subjects inserted right after artificial abortion were selected as the observation group and 80 female subjects inserted during the period of regular menstruation as the control group. Follow-up was performed at one year after insertion. Contraceptive efficacies and side effects were compared between two groups.No pregnancy was found in both groups. No mirena expulsion occurred in neither groups. The continuation rates were 100%and 95%in the observation and control groups respectively (P0.05). The rates of abnormal hemorrhage were 27.5% and 36.2% in observation and control groups respectively during the first three months (P0.05). And 22.7% and 23.3% subjects suffered amenorrhea respectively in the first year. No significant difference was found in such side effects as amenorrhea, weight gain, acne and swollen breasts between two groups (P0.05).Mirena is proved to be an excellent choice for contraception after artificial abortion. Secondary intrauterine surgery may be avoided. And its insertions immediately after artificial abortion or during the period of regular menstruation share the same efficacies.