Ulcerative Colitis is the abbreviation of chronic non-specific ulcerative colitis. It is a chronic inflammatory disease that involves rectum and colon with unknown cause. It belongs to diarrhea, dysentery, bloody stool, intestine wind or zang toxin in Chinese medicine. Modern medicine relates it to infection, genetics, allergy and autoimmune factors. Chinese medicine relates it to collection of damp and heat, qi stagnation blood stasis and deficient spleen and kidney. Although the treatment takes longer time, Chinese medicine is quite advantageous in treating this disease. This article provides reference for its cause, mechanism and treatment.