Objective:To explore the intrinsic risk factors in patients with ovarian hyperstimulation oocytes after letrozole to reduce ovarian hyperstimulation(OHSS)incidence of clinical effect.Method:A total of 86 high risk patients of OHSS in vitro fertilization cycles were prepared for embryo cryopreservation after oocyte retrieval,the patients in experiment group were treated with oral administration of letrozole after oocyte retrieval, and a systematic review of previous postoperative intravenous of gluconic acid calcium information to prevent ovarian hyperstimulation,the proportion of the incidence of OHSS of the comparison of the two programs,as well as in moderate and severe OHSS.Result:Of 86 patients in the letrozole prevention, estradiol levels decreased significantly,12.79% of the incidence of ovarian hyperstimulation,moderate and severe incidence was 2.33%,13.02% of the incidence of previous ovarian hyperstimulation moderate and severe incidence was 4.69%.Description letrozole can reduce the incidence of ovarian hyperstimulation.Conclusion:Providing letrozole for the high risk patients of OHSS after oocyte retrieval not only can prevent the occurrence of OHSS but also can reduce the incidence of moderate and severe OHSS.Letrozole can be used in the later clinical practice as the prevention of ovarian hyperstimulation.