Abstract： Objective To evaluate long term effect and related factors in patients with menorrhagia treated by microwave endometrial ablation(MEA).Methods Total of 334 women with menorrhagla were treated hy MEA,the range of age was from 29 to 59 years old.Among them,59 cases were complicated by adenomyosis.All the patients were followed up on the change of menstrual cycle.the amount of flow,improvement of anaemia and complication.Fifty-three women underwent outpatient diagnostic hysteroscopy,the biopsy tissue was taken from the endometrium for histopathological examination.The mean duration of follow-up was 64.7 months (3-96 months).Results The overall curative rate wag 91.3%(305/334),of which amenorrhea rate was 49.7%(166/334),menstruation reduction rate was 41.6%(139/334):71.1%(140/197) of the cases who previously had dysmenorrhea had relieved their pelvic pain and the satisfactory rate was 91.9%(307/334).Among patients＞40 years,92.9%(196/211) of operation effective rate,93.8% (198/211) of satisfactory rate and 64.9% (137/211) of amenorrhea rate were obtained.while patients≤40 years,88.6%(109/123) of operation effective rate,88.6%(109/123) of satisfactory rate and 23.6%(29/123) of amenorrhea rate were obtained.There was significant difierence in rate of operation effectiveness,satisfaction and amenorrhea (P＜0.05).Forty-two cases required subsequent treatment due to recurrence,of which 9 cases were given by secondary MEA and 33 cases (9.9%、33/334) underwent hysterectomy indicated by frequent menorrhagla,adenomyosis or leiomyoma.A completely destroyed endometrium was observed by hysteroscopy after MEA,pathologic characteristics of MEA showed two zones of necrotic tissue:the inner zone was coagulation necrosis and the outer zone of necrosis was hypocellular hyalinized myometrium.Conclusions MEA is the safe and efficacious management to treat menorrhagia.Incomplete removal of endometrium was the major reason resulting in postoperative recurrence.Young age and complicated with adenomysis were the main factors influencing long term clinical effect of MEA.