Objective To analyze the diagnostic results and imaging findings of high risk patients with placenta accreta by magnetic resonance imaging (MRI), and to provide theoretical basis for MRI diagnosis of placenta accreta. Methods The objects of this study were 70 patients with high risk of placenta accreta diagnosed in our hospital from December 2015 to December 2016, all patients underwent routine MRI examination after selection, and the results of MRI image analysis were recorded in detail. The diagnostic sensitivity and specificity of three types of placenta accreta, namely adhesive placenta, penetrating placenta, and implanted placenta, were analyzed by using results of MRI or pathological diagnosis as the gold standard. The imaging findings of MRI in some patients were analyzed. Results The MRI imaging findings of placenta accreta mainly showed that the unclear demarcation between myometrium and placenta, and the thinning of local uterine wall. T2WI images showed there were black stripes in the placenta, the lower part of the uterus was bulging, the uterus and placenta interface had multiple tortuous vascular, and bleeding or hematoma happened at the junction of the uterine wall and placenta, and bladder wall were interrupted. There were 40 cases of placenta free accreta, 6 cases of adhesive placenta accreta, 19 cases of implanted placenta accreta and 5 cases of penetrating placenta accreta diagnosed by MRI. There were 37 cases of placenta free implantation, 13 cases of adhesive placenta accreta, 17 cases of implanted placenta accreta and 3 cases of penetrating placenta implantation diagnosed by pathological diagnosis. The overall diagnostic sensitivity of placenta accreta was 66.67%, with a specificity of 83.78%, the Youden index was 0.50. The sensitivity, specificity and Youden index of adhesive placenta accreta were 46.15%, 98.25%, 0.44, respectively. The diagnostic sensitivity of implanted placenta accreta was 82.35%, specificity was 90.57%, and Youden index was 0.73. The diagnostic sensitivity, specificity and Youden index of penetrating placenta accreta were 66.67%, 95.52%, 0.61, respectively. Conclusion High risk patients with placenta accreta by MRI has a variety of characteristics of imaging findings, MRI has higher diagnostic sensitivity for implanted placenta, and can be used for the preliminary diagnosis of placenta accreta in high-risk patients.