In the present study, the surface modification of the PEBA membrane was done using amine compounds to improve the separation properties of carbon dioxide gas. The process of the surface modification of the membrane was performed in two stages. In the first stage, isocyanate, and the second stage, an amine solution was used to modify the membrane’s surface. The parameters such as process temperature, duration of each stage of the surface modification process, and concentration of amine solution in the second stage were optimized. Ethylenediamine, diethylenetriamine, tri ethylene tetra amine with different chain lengths were used to modify the surface of PEBA membranes. Also, to investigate the effect of toluene on a pure membrane separately, the membrane was immersed in the same conditions as the process of the surface modification of the first stage and the second under nitrogen medium. For membranes immersed in a solvent, the permeability of all gases except nitrogen increased. Also, the diffusion coefficient of all gases decreased and their solubility increased. According to the results of the ATR analysis, phase separation of the modified sample increased and therefore the role of solubility as the main mechanism of permeability became obvious. The results of ATR and the water contact angle indicated that the concentration of the amine groups on the surface of the membrane increased and the wettability of the membrane was improved. Also, it was observed that grafting process efficiency and grafting density have also been increased by increasing the concentration of the amine groups on the surface of the membrane. Solubility coefficient of the carbon dioxide increased due to its high density and polarity compared to other gases and its diffusion coefficient decreased