Rectal cancer is generally considered to be inherited for two generations. Rectal cancer is hereditary, and about 20%-30% of patients are related to heredity. Compared with normal people, the risk of rectal cancer among first-degree relatives and second-degree relatives is significantly higher, while the risk of rectal cancer among second-degree relatives is not significantly different from that of normal people. If one first-degree relative, including parents, brothers, sisters, children, etc., has rectal cancer, one’s risk of developing rectal cancer increases, and this risk is further increased if one first-degree relative and one second-degree relative both have rectal cancer. Since many rectal cancers evolve from adenomas, those who have first- or second-degree relatives with rectal cancer need to undergo e-colonoscopy and early detection and removal of adenomas to prevent the occurrence of rectal cancer.