A pseudo-homogeneous model for the cathode catalyst layer performance in PEM fuel cells is derived from a basic mass-current balance by the control volume approach. The model considers kinetics of oxygen reduction at the catalyst/electrolyte interface, proton transport through the polymer electrolyte and oxygen diffusion through porous media. The governing equations, a two-point boundary problem, are solved using a relaxation method. The numerical results compare well with our experimental data. Using the model, influences of various parameters such as overpotential, proton conductivity, catalyst layer porosity, and catalyst surface area on the performance of catalyst layer are quantitatively studied. Based on these results, cathode catalyst layer design parameters can be optimized for specified working conditions.