Through a mathematical modeling of Raney nickel hydrogen electrodes for AFCs, the distributions of electrolyte concentration, local overpotential and local current density in the catalyst layer, which are not experimentally measurable, were investigated. Also, we have studied the effects of microporosity and exchange current density on the electrode performance at the various thickness of catalyst layer. The results showed that the difference of the electrolyte concentration, the local overpotential and the local current density between electrolyte side and gas diffusion layer side increased with increase in catalyst layer thickness and overpotential. The closer to the electrolyte side, the more rapid the reaction rate in the catalyst layer was. When the thickness of the catalyst layer was less than about 0.1mm, the microporosity of the catalyst layer had little effects on the electrode performance. However, as the thickness increased, it increased electrode performance. An increase on exchange current density reduced the active thickness, but, increased the electrode performance regardless of the catalyst layer thickness.