In this study, the comparative advantage of main agricultural products and its relation to cropping pattern was studied in Ilam Province. For data analyzing the comparative advantage and government policies effects indices, Policy Analysis Matrix (PAM) were used. The obtained results for the comparative advantage indices of Domestic Resource Cost (DRC), Social Cost Benefit (SCB) and Net Social Profitability (NSP) show that production of irrigated wheat, dry-farming wheat and dry-farming barely has not comparative advantage in Ilam Province but the production of irrigated barely, corn, dry-farming pea, dry-farming lentil, watermelon, cucumber and tomato have comparative advantage in Ilam Province. In addition, the obtained results for NPIC index show the Nominal Government Protection of inputs in all products. Also, Nominal Protection Coefficient index indicated that nominal market protection of products like wheat (irrigated and dry-farming) and barely (irrigated and dry-farming) was positive and those of other products were negative and the Effective Protection Coefficient for wheat and barley had the highest values. The results showed that the existing cropping pattern was not allotted with comparative advantage but is related to the effective protection coefficient