Inflammatory diseases of rectal mucosa may cause cancer, and the specific reasons are analyzed as follows: First, inflammatory diseases of rectal mucosa mainly include chronic inflammation, acute inflammation and granulomatous inflammation, etc. If patients with acute inflammation are treated actively, they can be completely cured; however, if chronic inflammation is not treated effectively, long-term inflammation stimulation will lead to the occurrence of heterotypic change of intestinal mucosal epithelial cells and structural change, thus it can cause cancerous changes of rectal mucosa; second, inflammatory diseases of rectal mucosa are accompanied by atypical hyperplasia or heteroplasia, including mild, moderate and severe. Secondly, the inflammatory disease of rectal mucosa will be accompanied by atypical hyperplasia or atypical hyperplasia, and atypical hyperplasia includes mild, moderate and severe, mild atypical hyperplasia can be cured, and a part of moderate atypical hyperplasia can be reversible, and a part of it develops into severe atypical hyperplasia, which can easily become cancerous; thirdly, long-term chronic inflammation of intestinal mucosa will be accompanied with polypoid hyperplasia or adenoma. Polypoid hyperplasia or adenoma formation, and its chorionic gland tubular adenoma is very closely related to colorectal cancer, which is prone to cancer. Therefore, inflammatory diseases of rectal mucosa should never be neglected, and must be treated actively and standardized, otherwise there is a possibility of cancer.