The aim of this study was to determine the effect of 80 mg oral curcumin capsule, made by Eksir Nano Sina Company, on treatment of oral lichen planus of patients referred to center of oral and maxillofacial disease of guilan dentistry faculty. this study is accomplished, single blind, uni center, without any randomization and in 3th phase of clinical trial.13 patients with oral lichen planus without any systemic disease will be enrolled in this study. Patients didn’t use local corticosteroid from 2 weeks ago and systemic corticosteroid from 1 last month they take a drug and then use oral curcumin for 1 month, once a day after breakfast. Pain, burning sensation and size of the lesions assess before taking drug, and at the end of 1,2,4,8 weeks after treatment. Inclusion criteria are patients with oral lichen planus, who are volunteer and confirmed by histopathological evaluation. exclusion criteria is pregnant women, breast feeding women, patients who take corticosteroid, patients with peptic ulcer, gall-bladder stone, increased hepatic enzyme, and patients who take anti coagulation drugs, like warfarin. Treatment intervention is Consumption 80 mg oral curcumin capsule once a day for 1month. Primary outcome measure is pain and burning sensation of lesions, and secondary outcome measure is size of the lichen planus lesions.