Over the years, producing hydrogen by methane steam reforming (MSR) process in membrane reactor founds high attractions. Hydrogen permselective Pd-Ag membrane shows the best performance for pure hydrogen production. In the present study, the modeling of natural gas steamreforming in the tubular Pd-Agmembrane reactor for producing COfree hydrogen has been performed. The proposed model has been evaluated by some experimental data which obtained from a literature. The results confirmthat the experimental data can be simulated by the proposed model with an acceptable accuracy. Effects of various operating parameters such as pressure, temperature, steam to methane ratio in the feed, membrane thickness as well as different flow configuration of reactants and sweep gas on the amount of methane conversion, hydrogen production and hydrogento- carbon monoxide ratio have been investigated and their optimumvalues have been determined. The novelty of the present study is investigating the effect all of the operational conditions on the process by simple mathematical modeling, which not to be considered in any previous study. Moreover only some qualitative studies about optimal operational conditions ofMSR process have been done. Performed analyses confirmthat increasing the steam-to-methane ratio in the feed, temperature as well as pressure of the reaction zone and reducing the thickness of membrane can increase the methane conversion and hydrogen production.