Abstract： Objective To investigate the therapeutic effect of anchor?fixed Mirena(LNG?IUS)in the treatment of large adenomyosis. Methods Forty patients with large adenomyosis were randomly divided into two groups. The study group was treated with anchor?fixed Mirena,and the control group was pretreated with Leuprolide acetate(GnRH?a)for 3 months,and Mirena was used after the uterine size was reduced. After 12 months of follow?up,the dysmenorrheal degree,menstrual flow volume,uterine size,and adverse reactions at 1,3,6 and 12 months after intrauterine placement of Mirena were compared between the two groups. Results Both the study group and the control group showed a decreasing trend of dysmenorrheal degree and menstrual flow volume with the increasing time,and those in the two groups fell to the same level at 12 months. The uterine size in the study group continued to decrease. In the control group,the uterine size decreased more significantly than that in the study group at 1 month,and the change was stable between 3 and 6 months,whereas the size decreased after 6 months. There was no difference in the uterine size at 12 months between the two groups. In terms of low estrogen,the study group performed better than the control group,whereas there was consistency in the incidence of other adverse reactions between the two groups. Conclusion:The efficacy in the GnRH?a+Mirena group is better than that in the anchor?fixed Mirena group in the early stage of treatment,whereas the long?term efficacy tends to be consistent. Anchor?fixed Mirena may replace GnRH?a+Mirena in the treatment of large adenomyosis.