Objective To explore the MRI findings of placental protusion sign in predicting postpartum hemorrhage in patients with placenta previa.Methods Totally 354 placenta previa patients with whole clinical data underwent MR scaning 2 weeks before operation.Association of postpartum hemorrhage and placental protusion sign was analyzed.Results Among 354 patients with placental previa,the age of the pregnant women (x2 =4.34,P=0.04),gestational age at delivery (x2 =5.19,P=0.02) and the number of cesarean sections (x2 =44.85,P＜0.01) had associated with postpartum hemorrhage.Eight cases had placental protusion sign in MRI,while 6 cases occurred postpartum hemorrhage.The incidence of postpartum hemorrhage was 75.00％ (6/8) and 12.72％ (44/346) in patients with placenta accreta and with placental abruption,respectively (x2 =20.14,P＜0.01).The sensitivity,specificity,odds ratio (95％ confidence interval) and positive likelihood ratio of predicting postpartum hemorrhage was 12.00％ (6/50),99.34％ (302/304),20.59 (4.03,105.23) and 15.68,respectively.Conclusion MRI placental protrusion sign has important clinical reference value in predicting postpartum hemorrhage.