Rectal cancer is the fifth most common malignant tumor in China, and the mortality rate is also the fifth highest. In recent years, the incidence of rectal cancer is still rising due to changes in dietary habits. Because of the variety of treatment strategies, accurate preoperative TNM staging of rectal cancer is the key to the best clinical treatment and prognosis assessment. Endorectal ultrasound (ERUS) is a fast, safe and accurate imaging method for preoperative evaluation of tumor staging for rectal cancer. For the detection of the depth of tumor invasion and recurrence of rectal cancer after operation, the diagnostic accuracy of ERUS was higher than CT, and is equivalent to MRI. ERUS has been widely used in clinical treatment decision for patients with rectal cancer. However, the diagnostic accuracy of lymph node metastasis is still low. The new ultrasound technologies, such as contrast-enhanced ultrasound, ultrasound elastography and three-dimensional ultrasonography, are expected to improve the preoperative staging of rectal cancer, and have potential values in clinical application.