Objective To investigate the MR imaging findings of placental implantation and its prenatal diagnostic value. Methods Data of 105 patients with suspicion of placental implantation who had undergone MR and color Doppler ultrasound (US) evaluation in the second and third trimester gestation were collected retrospectively, including MRI findings and color Doppler ultrasonography of the placental implantation, the prenatal diagnosis, surgical evidence, pathological diagnosis, and so on. Taking surgical evidence or histopathology as reference, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy of MRI and US for the evaluation of placental implantation were determined. Results Of the 105 patients with suspicion of placenta implantation, 45 cases were consistent with pathology, including 22 cases of penetrating implantation, 13 cases of myometrium placenta implantation, and 10 cases of placenta adhesion; and 74 patients were assumed placenta accrata or suspected placenta accrata based on MRI. The sensitivity, specificity, positive predictive value, and negative predictive value of MRI and US for the evaluation of placenta implantation were 0.98 and 0.52, 0.48 and 0.86, 0.55 and 0.76, and 0.97 and 0.73, respectively(P<0.05). On MRI imaging, 51 patients showed lose of or ambiguous and blurry placental myometrial interface, 36 of them had placenta implantation, 15 of them did not have placenta implantation, and the accuracy was 71%. 3 patients with lose of the placental urinary bladder interface showing on the contrast-enhanced MRI were confirmed placenta implantation, the accuracy was 100%; the other abnormal findings on MRI were relatively rare, and they had limited value for the evaluation of placenta implantation. Conclusion Compared with color Doppler ultrasonography for the evaluation of placenta implantation, MRI has higher sensitivity and lower specificity. The lose of the placental urinary bladder interface on the contrastenhanced MRI is a reliable characteristic for the diagnosis of placenta implantation.