The following matters should be noted: 1. Before applying letrozole, we should strictly grasp the indications and contraindications and make sure that there is no ovulation and that the estrogen level is normal and the ovarian function is normal. 2. During the ovulation promotion process, the growth and development of follicles should be monitored by ultrasound. 3. It takes about 3 months or even 6 months for ovulation to be successful, so be patient. 4. Pay attention to whether ovarian hyperstimulation or premature ovarian failure will occur during letrozole ovulation promotion.