Bright red blood suspected on the 21st day of cesarean delivery needs to be treated according to the etiology, with contraction promotion treatment when caused by uterine dysplasia, medication when the uterine cavity is retained, and removal of the uterus if necessary. 1. Poor uterine regeneration: it can cause the thrombus formed on the placental attachment surface of the uterus to dislodge and the blood sinuses to reopen and lead to uterine bleeding, which can be diagnosed with the aid of ultrasound examination. It is necessary to give drugs such as hysteronin to actively promote contraction treatment, and give cephalosporin antibiotics to prevent infection treatment. 2. Uterine cavity residues: such as placenta, fetal membranes or meconium tissue, etc., can also cause re-vaginal bleeding, ultrasonography can be clearly diagnosed. It is necessary to follow the doctor’s instructions in the opening of intravenous access and the premise of blood preparation for uterine clearance, pay attention to the action of gentle, to avoid perforation, the cleared tissues sent to pathological examination, and given to the contraction of the uterus such as hysteronin and other promoters of contraction therapy and cephalosporin antibiotics to prevent infection treatment. 3. Poor healing of uterine incision: due to poor healing of uterine incision and infection of incision, vaginal bleeding will reappear 21 days after the operation, and the combination of medical history and ultrasonography can assist in the diagnosis. It is necessary to follow the doctor’s instructions to give contraction-promoting treatment such as hysteronin, cephalosporin antibiotics to prevent infection, and if necessary, need to carry out cesarean section or laparoscopy. Cesarean section 21 days suspected bright red blood when you need to go to the hospital in order to identify the cause and timely treatment.