Rectal palpation is the most important method to diagnose rectal cancer and is irreplaceable by any examination. For every rectal cancer patient as well as colon cancer, a rectal finger examination is required. For patients with rectal cancer, preoperative whole colonoscopy should be performed as much as possible, which not only clarifies the diagnosis and obtains the pathological type, but also avoids the missed diagnosis of repeat cancer. Enhanced CT of the whole abdomen should be a routine examination for rectal cancer to clarify whether there are lymphatic and distant metastases, and CT of the chest is recommended to exclude lung metastases if possible. PET-CT (whole body tumor examination) is feasible if available. Preoperative transanorectal ultrasound and MRI are important for preoperative staging and surgical planning of rectal cancer. In addition to routine blood biochemical examination, preoperative CEA, CA199 and other tumor markers (available in general hospitals) can not only assist in diagnosis, but also play a reference role in postoperative review and treatment.