Abstract: PURPOSE To investigate the miRNA (including miR-155, miR-146a and miR-146b) expression in peripheral blood mononuclear cells (PBNCs) or lesions tissues in oral lichen planus (OLP) patients and healthy controls and the relationship between miRNA and OLP clinical features. METHODS The expression of miRNA（miR-155, miR-146a and miR-146b）was assessed by quantitative fluorescent PCR in peripheral blood cells or lesions tissues in OLP patients and healthy controls. U6 was used as reference gene. Statistical analysis was performed with SPSS17.0 software package. RESULTS Real-time PCR showed that the expression of miR-155 in OLP PBNCs was significantly higher than that in controls, miR-155 expression in OLP lesions tissues was 7.0 times higher than that of PBMCs. Correlation analysis showed that the level of miR-155 expression in PBMCs was positively correlated with REU score(correlation coefficient R=0.887, P<0.01). There was no significant difference in miR-146a and miR-146b expression in PBMCs between OLP and control group. On the contrary, the miR-146a expression in OLP lesions tissues was significantly upreguated than that in control group (P=0.003).CONCLUSIONS The results indicated that miR-155 and miR-146a might play important roles in the pathogenesis of OLP and OLP is likely a chronic inflammatory disease characterized by local inflammation.