Plants exposed to air pollution show returnable and unreturnable biochemical and physiological alterations. So biochemical parameters can provide valuable information about physiological condition of plants that are subjected to air pollution. This study was performed to determine the effects of air pollutants on the amount of proline, protein, calcium and phosphorus in Medicago sativa and Phaseolus vulgaris leaf and root. We also investigated M. sativa and Ph. vulgaris resistance to the air pollution in Arak Oil Refinery area. The plant samples were collected from polluted and non polluted area and the amount of proline, protein, calcium and phosphorus in leaf and root of plants were determined. The results showed that air pollution led to a significant increase of proline in leaf and roots of both M.sativa and Ph. Vulgaris. Air pollution also led to a significant increase of protein concentration in M. sativa (leaf and root), but a significant decrease of protein concentration in Ph. vulgaris leaf and root. Concentration of calcium in M. sativa leaf and root under air pollution implied a significant increase. However air pollution caused a significant decrease of calcium in Ph. vulgaris root and no significant alteration of calcium rate in Ph.vulgaris root. Air pollution led to a significant increase of phosphorus rate in M. sativa root, but no significant alterations in M. sativa leaf, instead a significant increase of phosphorus rate in Ph. vulgaris leaf and root. In this study, increasing of protein and calcium in M. sativa plant was indicative of its resistance to the air pollution, and changes in biochemical parameters in Ph. vulgaris implied its sensitivity to the air pollution.