Mifepristone is a progesterone receptor antagonist, which can antagonize the action of progesterone in the body, prevent the implantation of a pregnant egg, terminate early pregnancy and induce menstruation. The effect of emergency contraception can reach up to five days, the earlier it is taken the better the effect, the later it is taken the greater the possibility of contraceptive failure, adverse reactions include excessive menstrual bleeding, some patients with early pregnancy have mild malignancy, vomiting, dizziness, headache, fatigue, diarrhea, anal swelling and rash after taking the pill, other rare adverse reactions include back pain, fever, chills, indigestion, insomnia, anxiety. Precautions are that the emergency contraceptive pill only has contraceptive effect on prior intercourse, no food or large amount of water two hours before and after taking the pill, and the emergency contraceptive pill cannot be taken more than once in a month or more than three times in a year, otherwise it will cause menstrual disorders, which can lead to infertility in serious cases.