Preoperative MRI evaluation of low rectal cancer in the total mesorectal excision ZHANG Xiao-peng,SUN Ying-shi. Medical Imaging Division, Peking University Institute of Clinical Oncology,Beijing Cancer Hospital and Beijing Institute for Cancer Prevention,Beijing100142,China Corresponding author: ZHANG Xiao-peng,E-mail:zxpabc@263.net Abstract The value of MRI in the preoperative evaluation of rectal cancer has been recognized internationally. As a result of total mesorectal excision (Total Mesorectal Excision, TME) is based on the anatomical basis of pelvic regional anatomy, the application of MRI in preoperative imaging clearly indicate that anatomical structure and its variation related to TME as well as its relationship with the tumor. We can correctly identify and grasp the TME-related MRI signs which will help the surgeon realize the lesions well before the operation. This article from the perspective of TME relevant anatomy imaging and MR signs, preoperative MR staging of rectal cancer, the preoperative judgement of circumferential resection margin and MR imaging technology to make a systematic elaboration and conclusion, with a view to help the surgeon apply and master preoperative MR rectal examination.