Abstract：From the study of the related works of LI Dongyuan，it is found that the pathogenesis of ulcerative colitis and the yin-fire theory have something in common. Starting from this，the etiology，pathogenesis and therapeutic characteristics of yin- fire are discussed， and the correlation between the yin- fire theory and the location， pathogenesis and clinical manifestation of ulcerative colitis is analyzed. In terms of treatment principles，the top priority should be given to balance the tip or root as well as urgent or moderate conditions，healthy or pathogenic qi as well as mild or severe conditions，and routine or paradoxical treatment. In terms of treatment methods，the main treatment should be upraising the middle qi with sweetwarm medicinals，supplemented by draining fire with sweet- cold or bitter- cold medicinals， and dispersing with wind medicinals can also be applied according to specific conditions. It is believed that there are definite curative effect and clinical values in the differentiation and treatment of ulcerative colitis by yin- fire theory which may become a new direction in the treatment of the disease.