Leukorrhea is a female vaginal secretion, which is a mixture of vaginal mucous membrane exudate, cervical canal and endometrial gland secretions, etc. Its formation is related to the action of estrogen, which plays the role of lubrication and protection of vaginal surface. Normal leucorrhea is white paste or egg white like, highly viscous, without fishy odor, small amount and no adverse effect on women’s health, called physiological leucorrhea. Due to the action of the pelvic floor muscles, the female vaginal opening is closed and the front and back walls are tightly packed. The moisture in the leukorrhea keeps the vagina moist. This moist environment reduces the friction between the front and back walls of the vagina and protects the vaginal walls from damage. At the same time, this moist state makes women’s vagina lubricated and elastic, which helps to improve the quality of sexual life. The leukorrhea is rich in glycogen, which is produced in large quantities by Lactobacillus vaginalis, making the vagina acidic (pH 4-5) and inhibiting the growth of various pathogenic bacteria. This natural physiological effect is called vaginal self-cleaning. Abnormal leukorrhea refers to an increase in secretion or abnormal nature. When the immune system is low, endocrine hormones change, or external factors such as tissue damage or sexual intercourse disrupt the ecological balance of the vagina, these resident flora will become pathogenic, and if inflammation or cancer occurs in the reproductive tract, the amount of leucorrhea will increase significantly and the traits will change, which is called pathological leucorrhea.