A sudden stream of fresh blood 15 days after delivery may be caused by poor uterine recuperation and uterine cavity residue. 1. Poor uterine regeneration: Generally, post-partum bloody discharge lasts for 3~4 days, but when there is a sudden flow of fresh blood 15 days after delivery, it may be caused by poor uterine regeneration, which may cause incomplete attachment of the placenta’s adherent surface and lead to dislodgement of the thrombus and reopening of the blood sinuses, resulting in uterine bleeding. The diagnosis can be clarified by ultrasonography, etc. 2. Uterine residual: when there is a combination of placenta and fetal membrane residual after delivery, when the residual tissue is degenerated, necrotic and detached, it can expose the blood vessels at the base and cause vaginal bleeding again. Examination reveals incomplete uterine regeneration, flaccid uterine opening and sometimes residual tissue. The diagnosis can be clarified by ultrasonography. In clinical practice, when there is sudden bleeding 15 days after delivery, it is necessary to go to the hospital in time to find out the cause and treat it actively.