The combined effects of NaCl-salinity and elevated CO₂ on the polypeptide levels in leaves of Aster tripolium grown under ambient (ca. 370 ppm) and elevated (520 ppm) CO₂ in different concentrations of saline irrigated water were examined by  two-dimensional   polyacrylamide gel electrophoresis. Silver nitrate stain gels were analyzed to identify changes that resulted when plant grown in  the presence of 375 mM NaCl  at ambient CO₂ level. The protein patterns for control and salt-stressed seedlings were qualitatively changed. This observation was mainly noticeable in young leaves which was not exposed to salinity stress. It is shown more polypeptide proteins through wide range of pH. In contrary,  leaves exposed to salinity stress revealed narrow polypeptide pH range proteins. Also, the control old leaves which was not exposed to salt stress showed limited pH range and lower polypeptide numbers compared to young leaves.                 The effect of NaCl on peroxidase activity under 0,125,250, 375 and 500 mM NaCl  was studied at the ambient CO₂ and elevated CO₂ levels. Peroxidase activity increased under NaCl salinity and the degree of elevation in the activity was salt concentration dependent. Nevertheless, a great activity was  recorded in stressed leaves comparison to control leaves. Furthermore, peroxidase activity was changed to lower activity in high level of CO₂ corresponding to ambient level of CO₂ The study revealed that Aster tripolium showed distinct differences in peroxidase activity behaviour under different environmental condition. The correlation coefficient between peroxidase activity under different salinity stress and high  level of CO₂ was strongly negative correlation, which means that  plant will not reveal stress response of peroxidase activity under elevated CO₂. Lowering of peroxidase activity under both salinity stress and higher level of CO₂ indicate to the important and unique role of halophyte  i.e. Aster tripolium in this study for removing, cleaning and remedy environmental air from higher level of CO₂ and decrease the green house effect.