The difference between the long and short regimens lies in the timing of the down regulation. Generally, the long regimen is chosen to inject long-acting down regulation drugs 7 days after ovulation in the last menstrual cycle, and then start ovulation promotion with drugs on the 3rd day of menstruation, while the short regimen is usually performed on the 3rd day of menstruation with both down regulation and super promotion, and generally short-acting down regulation drugs are chosen. Depending on the patient’s ovarian function, the choice of long or short regimen is made.