Oral submucous fibrosis(OSF) is a chronic and progressive oral mucosal disease with cancerous tendency.This paper discusses TCM pathogenic mechanism of OSF based on the therapeutic effect and pathogenic characteristics of the disease. The etiology of OSF is closely related with totoxic invasion, integration of phlegm and blood stasis, and Qi deficiency. The "strengthen body resistance and eliminating evil" combined with "remove blood stasis and reducing phlegm" methods are taken in clinic, which can improve the clinical sympt...