There is a high incidence of rectal cancer in developed countries, there is an increasing trend in China.Apart from a very early rectal cancer with local excision, the treatment of rectal cancer is still radical surgery.TME(total mesorectal excision) surgery has been shown to reduce the local recurrence rate of rectal cancer, but the surgery is largely dependent on the accurate preoperative evaluation of the extent of tumor.The possibility of distant and local recurrence continue to threaten the lives of cancer patients.TNM staging, evaluation of tumor's response and recurrence monitoring, are all important factors for clinicians to develop the treatment program and make prognosis, and now emerging as imaging research focus.