Objective To evaluate the diagnostic value of MRI in different types of prenatal placenta and the diagnostic efficacy of MRI image. Methods The imaging and clinical data of 99 cases with suspected placenta implant were reviewed. The pathological results and the intra-operative diagnosis was used as gold standard. The prenatal MRI findings of different types of placenta were compared and the diagnostic efficiency of MRI signs was analyzed. Results The accuracy of MRI diagnosis of placenta implant was 74.7%, The accuracy of diagnosis of adhesion, implantation and penetration of placenta were 73.6%, 90.9% and 93.9%, respectively. Among the MRI signs of placenta implant, the low signal disappearance of uterine matrix layer, multi-circuity and flow void in placenta, thinning of the myometrium focally and interrupted, placental ectasia focally, the swelling of the lower uterine segment, the statistical differences was found between the implanted and non-implanted groups (all P<0.05). Conclusion MRI has high specificity, multi-circuity and flow void in placenta, thinning of the myometrium focally and interrupted, placental ectasia focally，swelling of the lower segment of the uterus are valuable diagnostic signs. Among those, the diagnosis value of the low signal disappearance of the uterine matrix is the most valuable.