Abstract: Since Ye Tianshi is a representative of Wumen Medical School， this paper systemically summarizes Dr. Ye’s thoughts on collateral disease theory and its application in the clinical practice by analyzing his master work Case Records as a Guide to Clinical Practice， where he puts forward the famous ideas of long illnesses entering into collaterals and long pains into collaterals， with etiology and pathogenesis of collateral diseases being expounded and treatment principles of dredging collaterals with herbs of spicy flavor， ants and insects or by removing blood stasis as well as prescriptions being advocated on the basis of experience from predecessors. Hence， a deep exploration of his collateral disease theory plays a significant role in improving the clinical curative effects on miscellaneous diseases.