Function-preserving surgery for ultra-low rectal cancer is performed when the tumor can be completely removed while preserving the anus as well as bowel and sensory functions. However, it may lead to peripheral nerve damage, anastomotic stenosis and scar formation in the surrounding tissues. Function-preserving surgery for ultra-low rectal cancer is to preserve anal sphincter function under the premise of completely removing the tumor. Not only the anus is preserved to keep the continuity of the digestive duct, but more importantly, the bowel function as well as the sensory function is preserved. Although function-preserving surgery for ultra-low rectal cancer preserves the anatomical continuity of the bowel, the procedure removes some or the receptors for the bowel reflex arc. The surgery may also result in peripheral nerve damage, anastomotic stricture and scarring of the surrounding tissue, which may result in symptoms such as urgency, frequency and gas incontinence. The discomfort generally improves over time in most patients. Patients should have good bowel habits, adjust their diets to ensure the smooth flow of stools, and have regular checkups after function preserving surgery for ultra-low rectal cancer.