Abstract: 【Abstract】 Letrozole (LE)?was?a?third-generation?aromatase inhibitor (AIs, CYP19),?which is?a kind of?artificially synthesized triphenyl quinoline derivative.?It?is?first formally used in?the?clinical treatment of ovulation induction in foreign countries in 2001.?Polycystic ovary syndrome?(PCOS) is a reproductive endocrinology and metabolic disorders commonly found in?the?women of reproductive age, with the main character of ovulation, which is one of the direct causes of infertility.Due to some side effects, there were?some limitations?to?the?clomiphene citrate (CC)?drug which?is?clinically?used?as the first choice in?the treatment of ovulation induction. The study found that?LE can promote endometrial growth?in?the?infertility treatment?of?PCOS women,?which not only has?no adverse effects on cervical mucus?but also?provides?good conditions for embryo implantation. Also,?LE?was?better than CC?in the aspect of?ovulation rate and birth rate. Perhaps, there were some differences in?abortion rate, multitle-gestation pregnancy rate and the fetal safety, but the current study?had?no?statistically significance.Therefore,LE may?replace?CC?to become?the?first-line ovulation?induction?drug?in?the?infertility treatment?of?PCOS women.

Key words: 【Keywords】Letrozole, ?Clomiphene citrate, ?Polycystic ovary syndrome, ?Infertility, Ovulation induction