Objective:To study the expression and significance of STAT3 in Oral Lichen Planus(OLP)of different clinical types.Method:The immunohistochemical assay was used to detect 10 cases of normal oral mucosa,30 patients with non-erosive OLP and 20 patients with erosive OLP of STAT3 protein expression in the lesions.Result:STAT3 was expressed in the cell cytoplasm,and nuclear expression was also found in some cells in OLP.In the cases of normal oral mucosa,nonerosive and erosive OLP,the rate of STAT3 expression in epithelial layer was 30 %(3/10)、75.86 %(22/29)、93.75 %(15/16),respectively;in lamina propria,0 %(0/10)、65.52 %(19/29)、100 %(16/16),respectively;There were statistical significances of STAT3 expression between normal oral mucosa and non-erosive OLP as well as erosive OLP in epithelial layer(P 0.05),while no statistical significances of STAT3 expression were found only between non-erosive and erosive OLP in lamina propria(P 0.05).Conclusion:The over-expression of STAT3 played an important role in the inflammation progression of the OLP's epithelium,and the study of STAT3 expression was useful for detection of the pathogenesis and early diagnosis of OLP.