The main effect of levonorgestrel emergency contraceptive pill is contraception, it is from the following aspects to achieve the effect of contraception: 1. levonorgestrel is an efficient progestin, can make the cervical mucus become thicker, affect the sperm penetration, so as to achieve the effect of contraception. 2. levonorgestrel can inhibit female ovulation, no egg discharge patients can not conceive. 3. levonorgestrel can make the patient’s 4. levonorgestrel, a highly effective progestin, can disrupt the normal oscillation of the fallopian tubes and the oscillation of cilia, which can disrupt the transportation of fertilized eggs, thus achieving the effect of contraception.