Objective To investigate the predictive value of cervical canal length measured by transvaginal ultrasound for emergency early cesarean section of pregnant women with placenta previa.Methods 128 pregnant women with placenta previa who delivered in the hospital were selected as the research subjects between March 2019 and August 2020. According to the time of cesarean section, the pregnant women were divided into emergency early cesarean section group (78 cases) and term cesarean section group (50 cases). All pregnant women received transvaginal ultrasound examination in the third trimester of pregnancy to measure the cervical canal length. The clinical data and cervical canal length of the two groups were compared. The ROC curve was used to analyze the predictive value of cervical canal length for emergency early cesarean section of pregnant women with placenta previa. Logistic regression analysis was performed to screen the risk factors for emergency early cesarean section of pregnant women with placenta previa. The pregnancy outcomes and neonatal outcomes of the two groups were compared. Results The proportions of pregnant women with miscarriage history and complete placenta previa in the emergency early cesarean section group were higher than those in the term cesarean section group (P<0.05). The cervical canal length measured by transvaginal ultrasound of the emergency early cesarean section group was smaller than that of the term cesarean section group (P<0.05). ROC curve analysis found that the best cutoff value of the cervical canal length measured by vaginal ultrasound was 25 mm. When the cervical canal length was shorter than 25 mm, the predictive value in emergency early cesarean section of pregnant women with placenta previa was the highest, with sensitivity of 85.90% and specificity of 82.00% (AUC=0.920, 95%CI=0.8740.966). Complete placenta previa (OR=2.452) and cervical canal length≤25 mm (OR=3.789) were risk factors for emergency early cesarean section of pregnant women with placenta previa (P<0.05). There were no statistically significant differences in the incidence of postpartum hemorrhage, blood transfusion volume, and the incidence of neonatal asphyxia between the emergency early cesarean section group and the term cesarean section group (P>0.05). The proportion of low birth weight infants in the emergency early cesarean section group was higher than that in the term cesarean section group (P<0.05). Conclusion The cervical canal length measured by transvaginal ultrasound is of high predictive value for emergency cesarean section of pregnant women with placenta previa, which is helpful to strengthen perinatal management and avoid adverse pregnancy outcomes.