The principle of letrozole ovulation promotion is that as an aromatase inhibitor, it inhibits the conversion of androgens to estrogens, causing estrogen levels to decrease, and then acts on the pituitary gland of the hypothalamus through a positive feedback mechanism to secrete follicle stimulating hormone (FSH) and increase its release to promote the development and discharge of follicles. It is mainly used for patients with a healthy feedback mechanism of the hypothalamic-pituitary-ovarian axis and a certain level of estrogen in the body. Adverse effects include nausea, headache, dizziness, bone pain, arthralgia, hot flashes, vaginal bleeding, weight gain, etc. The medication should be used in accordance with medical advice after detailed examination by a physician and is not recommended to be used blindly.