Leukorrhea is a mixture of vaginal mucous membrane exudate, cervical canal and endometrial glandular secretion, etc. Its formation is related to the action of estrogen in the body. The normal leucorrhea is generally a highly viscous thin paste or egg white, after the onset of menstruation the body’s estrogen level is relatively low, the amount of mucus secreted by the cervical canal is relatively small, but with the development of follicles, the body’s estrogen concentration is increasing, the amount of cervical mucus secretion is also increasing, to ovulation will become thin and transparent, the degree of drawing is relatively large, the long degree of drawing can be more than 10cm. This situation is related to the high estrogen level in the body and can also be a manifestation of ovulation. After ovulation, the estrogen level decreases and the degree of stretching is poor and easily broken.