To observe the relativity of mitochondrial structure damage and the express of inflammatory factor in UC rats，to analysis the curative effect of Yiqi Jiedu formula(Qi-tonifying and toxicity-relieving formula)in acute and chronic phase，and to discuss the regulatory mechanism of Yiqi Jiedu formula in inflammatory factors and mitochondrial structure in different phases.Methods:The experimental rat models with ulcerative colitis were set up by immune complex method(sensitization with rabbit mucous membrane of colon and coloclystering with TNBS and 50% alcohol).One hundred rats were randomly divided into the normal group，model group，Yiqi Jiedu group and mesalasize group.Colon samples were taken from the four groups at the 1 st day，14th day and 56th day respectively of and the ultra-microstructure of rat colonic mucosal epithelial cells were observed under electron microscope.The colon mitochondria with Flameng score system were graded and the expressing level of TNF-α and ICAM-1 in mucous membrane of colon were tested by immunohistochemical method.Results:The damage of ultra-microstructure in mucous membrane of colon cells existed in the whole UC process，especially the mitochondria was more lasting and serious.The expresses of TNF-α and ICAM-1 in colonic mucosa increased obviously and descended with the progression，but both of which are higher than those of the normal group in chronic phase.The damage of the mitochondria mainly synchronizes with the express of TNF-α in colonic mucosa in the whole progression of UC.To some extent，mesalazine had some repairing effects in acute phase，but poor efficacy in chronic phase，no apparent recovery of mitochondria in chronic phase.In the respects of regulating TNF-α and ICAM-1，the decline rate by mesalazine in acute phase was significantly over Yiqi Jiedu formula.While in chronic phase，Yiqi Jiedu formula overtook mesalazine，with the decline rate over mesalazine，which was closer to normal level.Conclusion:The damage of mitochondrial structure in chronic phase may correlate with the lasting high express of inflammatory factor，and which maybe the potential cause to palindromia and the damage of colonic mucosa.Mesalazine may rapidly control the acute exacerbation of inflammation，while the Yiqi Jiedu formula is better in controlling the lasting chronic inflammation，especially in lastingly repairing the damaged mitochondria.It shows great superiorities in anti-palindromia in chronic phase.