Objective Clinical risk factors and ultrasound signs were used to predict the risk of severe intraoperative bleeding in dangerous placenta previa，and a risk model was established.Methods 80 patients with dangerous placenta previa admitted to Beijing Chaoyang Hospital and Beijing Obstretrics and Gynecology Hospital of Capital Medical University from August 2018 to December 2023 were retrospectively analyzed.The amount of intraoperative bleeding ＜ 1000ml was defined as light bleeding.If the amount of intraoperative bleeding is ≥1000ml，it is severe bleeding.The clinical risk factors and ultrasound signs were compared between the two groups.A risk model of severe intraoperative bleeding in patients with dangerous placenta previa was established based on clinical risk factors and ultrasound signs.Results In 80 cases，27 cases were in moderate and 53 cases in severe group.In the mild group，12 cases（44.4%） had no PAS，13 cases（48.1%） had accreta，and 2 cases（7.4%） had increta.In the severe group，11 cases（20.8%） accreta，24 cases（45.2%） increta，and 18 cases（34.0%） percreta.A total of 7 patients underwent hysterectomy，all of whom were in the severe group.There were significant differences in the number of cesarean section，disappearance of retroplacental space，placental lacunae，abundant blood flow at uterovesical junction，interruption of bladder line and cervical involvement between the two groups（p<0.05）.Binary Logistic regression analysis showed that the number of cesarean section and abundant blood flow at the uterovesical junction were independent risk factors for severe intraoperative bleeding(OR=10.560、15.831,P<0.05).Based on this，a risk model was established and the ROC curve of each independent risk factor and risk model was drawn.The AUC of the risk model was 0.787，which had better diagnostic performance than other independent risk factors（0.632、0.768，respectively）.Conclusion In the evaluation of severe intraoperative bleeding in patients with dangerous placenta previa，the number of cesarean section and abundant flow at the uterovesical junction were combined to establish a hemorrhage risk model，which has good diagnostic efficacy for severe hemorrhage.