Objective To analyze the performance of adsorbing CO2 with zeolite 5A molecular sieve in crew module. Methods Fitting analysis was based on experimental data of adsorbing CO2,O2 and N2 with zeolite 5A molecular sieve and the suitability of isotherm adsorbing equation of Langmuir,Freundlich and BET models to be conducted with Origin software. Then using obtained equations and competitive adsorbing theory,the adsorbed amounts of these three kinds of gas under competitive condition were calculated. Results The constants in equations for adsorbing CO2,O2 and N2 with zeolite 5A molecular sieve were determined,and adsorbed amounts for above three kinds of gases under competitive condition were calculated. Conclusion The adsorbed CO2 amount is affected by high fraction of N2. Therefore zeolite 5A molecular sieve should be modified technically so that its adsorption in N2 might be reduced to an ignored amount.