This study concerns palladium membrane reactors for methane steam reforming by means of mathematical modeling. In terms of similarity in reaction rate profiles, a whole reactor can be divided into three zones: I common to conventional and membrane reactors; II common to the co-current and counter-current membrane reactors; III characteristic of the counter-current membrane reactors. Although reaction rate decreased from the inlet in zones I and II, it increased in zone III. Furthermore, a part with apparently slow reaction and permeation was found in the profile for counter-current long reactor. The part is the end of zone II, which is normally seen in a co-current MR. It locates at the end of reactor in a co-current, however, in the middle of the reactor in a counter-current.