There are several reasons for the sour smell of leukorrhea: 1. It may be due to bacterial infection, such as staphylococcus, staphylococcus aureus, streptococcus pneumoniae, etc. When women are infected by these common bacteria, it can lead to acute or chronic inflammation of the vagina, which can subsequently lead to vaginal skin mucosa erosion and ulceration, while the metabolic waste of bacteria can also seep out to the surface of the vaginal skin mucosa. 2. It may be due to female endocrine dysfunction, because the formation of leucorrhoea is closely related to the endocrine system, if the endocrine system is abnormal, such as the secretion of estrogen, sex hormones and progesterone, the content of these hormones is reduced, which can also lead to leucorrhoea with a sour smell. 3. There are tumors forming, such as cervical tumors, endometriomas, mucus tumors in the uterine cavity, etc. can lead to a sour smell in the leukorrhea.