Oral lichen planus (OLP) is a T cell-mediated immune disorder, and we have indicated a Th1-dominated immune response in OLP. MicroRNA-155 (miR-155) could promote Th1 cells polarization. The present study aims to determine the role of miR-155 in immune response of OLP. The expression of miR-155 and the target mRNA was tested by Real-Time PCR. The serum levels of IL-2, 4, 10 and IFN-gamma were examined with ELISA. Furthermore, in vitro study was built to observe the function of miR-155 in erosive-type OLP (EOLP). Finally, we determined the expression and correlation of miR-155 and SOCS1 in EOLP CD4(+) T cells. The results showed miR-155 was high related with the disease severities. Besides, serum IFN-gamma was specifically increased in EOLP group, while IL-4 was decreased. In vitro studies showed miR-155 could reinforce IFN-gamma signal transducer, and the induction of IFN-gamma could also promote miR-155 expression in EOLP CD4(+) T cells. In addition, miR-155 levels were negatively related with SOCS1 mRNA expression in EOLP CD4(+) T cells. Our study revealed a positive miR-155- IFN-gamma feedback loop in EOLP CD4(+) T cell, which might contribute to the Th1-dominated immune response. Furthermore, miR-155 could be used for the evaluation and treatment of OLP.