Rectal cancer patients can have an MRI on the day they finish their course of radiation therapy. Rectal cancer patients can have MRI examination on the day of the end of radiation therapy course. MRI can understand the location of the tumor and its relationship with the surrounding adjacent structures, evaluate the invasion range of rectal cancer and whether the lymph nodes in the abdominal cavity are enlarged, etc., which can be used to assess the severity of the disease and guide the staging of the tumor. However, the definitive diagnosis of rectal cancer also relies on colonoscopy to obtain tissue specimens for pathological examination to clarify the tumor type. Then combine with CT, MRI and other auxiliary examinations to clarify the tumor staging and formulate reasonable treatment plan. Rectal cancer patients should actively cooperate with doctors and standardize treatment under doctors’ guidance.