Objectives: Today, oxidative stress as a predisposing factor in the pathogenesis of Chronic Obstructive Pulmonary Disease is known, although the correlation between chronic obstructive pulmonary diseases with antioxidants remains unclear. Design: So this study was to evaluate the effect of conjugated linoleic acid (CLA), as an antioxidant, on serum level of malondialdehyde (MDA),matrix metallopeptidase 1(MMP1), matrix metallopeptidase 2(MMP2), Leptin,Sirtuin 1,Interleukin 6 and Interleukin-1 beta (IL1β) as bio-marker for oxidative stress occurs. Setting and conduct: This double-blind prospective study on ninety cases of chronic obstructive pulmonary disease at the interval January 2015 to December 2015 in Imam Khomeini hospital in Ardebil is done. The provided forms containing demographic information, Chronic obstructive pulmonary disease Assessment Test (CAT), modified dyspnea scale (MMRC) and appetite questionnaire is completed. Then, spirometry and six-minute walk test is done. Then 3 cc of blood from patients to measure serum levels of Interleukin-1beta, malondialdehyde, matrix metallopeptidase 1(MMP1), matrix metallopeptidase 2(MMP2), Leptin,Sirtuin 1,Interleukin 6 and serum total antioxidant capacity is taken. Participants including major eligibility criteria: inclusion criteria include Chronic Obstructive Pulmonary Disease patients aged between 40-80؛ clinically stable disease with FEV1 less than 75% predict and exclusion criteria include female؛ any associated chronic diseases such as CAD and CKD...؛receiving any interacting drugs؛ abnormal chest x ray Intervention: The original drug (conjugated linoleic acid 3.2 g, soft gel 800mg four times in day) and placebo (soft gel four times in day) in equal numbers will be packed in similar package. Packets from one to ninety-numbered and randomly given to patients for six weeks.Six weeks after the intervention, again COPD Assessment Test (CAT), dyspnea scale (MMRC) and appetite completed questionnaires, spirometry and six-minute walking test was performed for the second time. During the intervention, the patient closely for possible side effects and medication use are followed. Main outcome measures (variables): blood sampling is repeated for matrix metallopeptidase 1(MMP1), matrix metallopeptidase 2(MMP2), Leptin, malondialdehyde (MDA) and Interleukin-1 beta (IL1β),Sirtuin 1,Interleukin 6 and total antioxidant capacity. Before entering the study, written informed consent was obtained from all patients