Abstract： The endogenous"five evils"are the comprehensive pathogenesis changes caused by abnormal physiological func-tions of Zang-Fu organs,meridians,Qi,blood and body fluid,which are closely related to the pathogenesis and pathological chan-ges of ulcerative colitis(UC).It is of great significance to explain the pathogenesis and treatment of UC in terms of internal damp-ness,internal fire,internal wind,internal cold and internal dryness in clinical theory research.The pathogenesis of UC caused by endogenous"five evils"and the corresponding treatment methods are mainly as the following.Internal dampness:There is internal phlegm and dampness,spleen deficiency and weakening Yang.The treatment is to invigorate spleen and Yang and to transport phlegm and dampness.Internal fire(internal heat):The fire-heat is endogenous,blood overflows and there is blood stasis ob-struction,and it is advisable to clear(deficiency)heat and dissipate fire(heat)as well as remove damp-heat and resolve blood stasis.Internal wind:There is the internal accumulation of liver wind and the wind damages the intestinal collateral,and the collat-eral is damaged and blood overflows.The treatment is to soothe liver and regulate Qi,clear intestines and disperse wind,cool blood and stop bleeding.Internal cold:There is Yang deficiency of spleen and kidney,cold coagulation and blood stasis.The treatment is to warm kidney and spleen,activate blood circulation and relieve pain.Internal dryness:Dryness damages the blood and body flu-id,and the intestinal collateral is lack of nourishing The treatment is to promoting fluid production and moistening dryness and nourish the intestines.In clinical practice,UC is not caused by a single pathogen,but can be a combination of the"five evils",and easily cause phlegm and blood stasis.Clinical treatment should be adjusted according to the syndrome.