Objective To discuss the diagnostic value of MRI for local lymph node metastasis and rectal cancer. Methods The clinical data of 180 cases of rectal cancer confirmed by pathology were selected in our hospital in April -2017 April 2015, there are complete MRI image data. With pathological diagnosis as the gold standard, the diagnostic accuracy of MRI for preoperative evaluation and local lymph node metastasis was analyzed. Results The accuracy of T≤2 in T stage of MRI was 88.9%, the accuracy of T3 was 82.1%, the accuracy of T4 was 86.7% , T staging total accuracy of 85.0%. N staging N0 accuracy 79.7%, N1 accuracy 64.9%, N2 accuracy 61.9%, N staging the total accuracy of 69.4%. The group of 180 patients pathological diagnosis showed that 102 patients with positive node, the negative in 78 cases, the sensitivity and specificity of preoperative MRI in diagnosing lymph node metastasis were 79.4% and 69.2% respectively. The false positive rate was 30.8%, the false negative rate was 20.6%, the positive predictive value was 77.1% and the negative predictive value was 72.0%. Lymph node metastasis MRI features: The lymph node metastasis was lobulated or burr-like, part of the lymph node signal has a non-uniform performance. Conclusion Preoperative MRI examination of the staging of rectal cancer has important value for preoperative evaluation of the disease and provide a basis for the development of treatment options, MRI has some value in judging the local lymph node metastasis of rectal cancer, but there are still some limitations, clinical practice should be combined with other imaging methods to improve the diagnostic accuracy.