The primary function of the ovaries is to produce eggs and secrete sex hormones. Well-developed follicles and an accurate ovulation date lay the foundation for eugenics and fertility. Ultrasound monitoring of follicles is often needed during the infertility diagnosis to see if there are normal follicles growing, developing and expelling in order to understand whether ovulation is normal. In case of ovulation disorders, follicular development monitoring is even more necessary when medication is administered to guide clinical use of medication, sex life, artificial insemination and follicular puncture. There are various methods to monitor follicular development and ovulation, among which ultrasound monitoring is the current preferred method for intuitive and accurate ovulation monitoring because it is intuitive, non-invasive, reproducible and easy to observe. Ultrasound monitoring of follicles can be performed by abdominal ultrasound or negative ultrasound, with the majority of clinical choices being negative ultrasound monitoring. ultrasound monitoring of follicles may seem cumbersome, but it is very important and has important clinical implications. Ultrasound monitoring of follicles is generally indicated for patients with regular menstrual cycles, and those with menstrual cycles not shorter than 21 days and not longer than 40 days can choose ultrasound monitoring of follicles for development, maturation and expulsion. If the menstrual cycle is longer than 40 days, endocrine examination can be performed 2-4 days into the menstrual cycle. Based on the endocrine results, menstrual regulation therapy and ovulation promotion therapy can be selected for the cause. The day of ovulation is usually about 14 days before menstruation. In women with regular menstruation, the luteal phase is fixed, while the follicular phase can vary in length. ultrasound monitoring of follicular development starts 16-18 days before the first day of the next menstrual period and is performed every 2-3 days. For each monitoring, observe the size and morphology of both ovaries, record the number and size of follicles, the thickness of the lining, and the day of menstruation. It is important to use ultrasound to monitor the detailed follicular development of infertile women to confirm whether they have matured follicles, whether they have ovulated and the time of ovulation, so as to provide a reliable basis for the clinical symptomatic treatment.