Secondary postpartum hemorrhage is caused by subinvolution of uterus, coagulopathy, infection or wound dehiscence of cesarean section incision, placenta increta, abnormalities of uterine vasculature, and so on. The precautions of secondary postpartum hemorrhage are using oxytocin appropriately, preventing uterine incision infection, following the cesarean delivery indication strictly, selecting the uterus incision reasonably, suturing the incision by anatomical structure, and monitoring the placenta increta patients closely by following up.