The incidence of breast cancer is growing rapidly and has attracted close attention. The causes of breast cancer are responsible for its development and are currently considered to be complex. For example, higher intake of high fat and low fiber diet, postmenopausal weight gain, smoking, radiation exposure, pesticides, adverse stimuli such as hormones and genetic factors. Clinical studies have concluded that the occurrence of breast cancer is very closely related to the estrogen level that accompanies women throughout their life, and there are many risk factors in marriage, fertility and sex. Early menarche (before the age of 12), late menopause (after the age of 50) and long menstrual period (more than 35 years) are recognized risk factors for the development of breast cancer. Some studies have reported that the risk of menarche is 2.2 times higher for those with menarche earlier than 13 years old than for those with menarche older than 17 years old; the risk of menarche is about 1 times higher for those with menarche older than 55 years old than for those with menarche younger than 45 years old. The incidence of breast cancer is significantly higher in women who are celibate, unmarried or unpregnant over the age of 40 or whose first child is older than 30 years old than in women who are normally married, and the incidence of breast cancer in women who have their first full-term child before the age of 25 is only about 1/3 of that in women who have their first full-term child after the age of 30. Women who give birth but do not breastfeed, or who breastfeed for a short period of time, or who breastfeed with only one breast, may also have an impact on the occurrence of breast cancer. Therefore, proper breastfeeding after childbirth can keep the mammary glands open and have a preventive effect on the occurrence of breast cancer. If a woman rarely breastfeeds or never breastfeeds, the risk of breast cancer will increase significantly. 3. Sexual life The quality of sexual life between husband and wife directly affects the physical health of the breast. In recent years, the incidence of lobular hyperplasia and benign and malignant tumors of the breast has increased rapidly, which has attracted the attention of the medical community. Eighty-six percent of women with lobular hyperplasia never have an orgasm during sex. If a woman is always sexually excited but cannot reach orgasm, her body will feel extremely uncomfortable and the unreleased sexual tension will easily turn into cramps and pain, which over time will produce psychological and pathological “depression” and lead to lesions in the breast tissue. Research on the psychological characteristics of breast cancer patients also shows that the level of depression and anger in breast cancer patients is higher than that of healthy people. Therefore, modern women should raise their awareness of self-care and promote late marriage and childbirth, but not too late, it is better for women to marry before 28 years old. It is important to promote a scientific lifestyle such as breastfeeding, reasonable diet and physical exercise, and to pay attention to keeping an open mind, avoiding depression and anger, and maintaining good physical and mental health, all of which are essential to prevent and reduce the incidence of breast cancer.