The premarital sex between unmarried men and women who have not fulfilled the marriage registration formalities is an extramarital sex that violates the legal principle of the unity of marriage and sex. The rising trend of premarital sexual experience is worldwide. Since 1960s, premarital sex has been rampant in western countries, and the number of unmarried mothers and children born out of wedlock has caused serious social problems. People who have a positive attitude towards premarital sex believe that premarital sex can happen as long as both men and women are happy. Sexual relationship or cohabitation is based on the constraints of traditional sexual morality. Most people in China hold a negative attitude towards premarital sex, but in real life, premarital sex exists in large numbers. There are several subjective factors that cause premarital sex: ① The two sides are too close in love to restrain their sexual impulse; During the period of love, one party is afraid of the other party's change of heart and deliberately causes sexual relations in order to achieve the purpose of marrying the other party; ③ Teenagers are out of curiosity and sexual experience. The social reasons for seeking marriage but not meeting the statutory conditions are as follows: ① The liberation of human nature, the change of marriage concept and the development of contraceptives have increased the tolerance of society for premarital sex, and greatly reduced the anxiety and anxiety of young men and women about sexual relations; ② The excessive exaggeration of love by mass media greatly enhances the sexual stimulation of young people; ③ There is a long period between the realization of sexual desire in the early stage of sexual maturity and the arrival of marriage age. The waiting period makes it possible to have sex earlier. (4) With the urbanization of society, the importance of family in the process of teenagers entering the society has decreased. ⑤ Sexual values and moral education cannot keep up with the needs of social development. Social supervision of sexual behavior weakens this harm. ⑤ Traditional morality has been destroyed, and the cornerstone of marriage and family relations has been destroyed. The initiators of premarital sex are mostly men, but the direct victims are women. Women who have premarital sex are not only under great pressure from public opinion, but also in China, few men are willing to marry women who have premarital sex as partners. When the man knows that the woman has such a problem, he will often immediately terminate his love relationship or seriously deteriorate his marriage relationship. The relaxation of interpersonal relationship in sexual behavior often leads to a rash attitude towards marriage. Some marriages are changed to "dew couples", and even after marriage, there will be hidden dangers. For example, some couples are suspicious of each other after marriage because of premarital sex, and suspect that the other party is having an affair. Some people have sex before marriage, but they don't change their bad habits after marriage, which leads to family breakdown. This has caused psychological pressure to the woman. Women often feel all kinds of pressure and accusations, resulting in inferiority complex. If she marries a man who has sex before marriage, her mind will gradually calm down as time goes by. If abandoned after pregnancy, it will have a great impact on her life, leaving dark clouds and trauma in her heart that can never be erased. She may be hostile to men and choose celibacy; Or change their moral values and "break the jar and break the fall"; Or escape from reality by suicide; Or rush to marry someone else to cover up ugliness. 4. Bring problems to fertility. Some people are infertile for life because of repeated abortion. Even if they have children in the future, they are prone to obstetric complications. Some children born out of wedlock are discriminated against by society because of premarital sex. 5. Unable to coordinate sexual relations. Many facts have proved that cohabitants before marriage did not show superiority in family life. Cohabitation before marriage often has only sexual relations but no economic and other relations, so this relationship is not stable. Sometimes there is another extreme change. It turns out that the relationship of mutual equality and free choice between two lovers was destroyed by premarital sexual relations. The man thinks that the woman can't live without herself, so he controls his attitude at will. On the contrary, the woman is committed to the other party, afraid or worried that the man will change his mind, so she has to tolerate it again and again. Even if the man has great shortcomings, some people have to get married because of pregnancy, not because of true love. It is inevitable that there is no tragedy after marriage. Examinations can easily spread diseases and endanger the health of both sides and the next generation. All landowners cannot be protected by law. Some bad guys play with women in the name of love and take the opportunity to avoid measures. Premarital sex is not recognized by law and morality. Premarital sex belongs to illegal cohabitation, which should arouse general concern. We should continue to publicize the marriage law, vigorously strengthen the education of socialist legal system and marriage ethics, and make people establish the concept of legal system. Only by registering marriage according to law can we generally understand the law. To live together legally, we should give necessary education and appropriate treatment to a few people who ignore the law and morality and live together illegally. In addition, what needs to be emphasized here is that the initiative to avoid non-violent premarital sex is in the hands of women. As a woman, to fully understand the harm of premarital sex, we need to respect ourselves, refuse the man's deviant request and prevent premarital sex.