A fully coupled numerical simulation is used to investigate the catalytic partial oxidation of methane over a honeycomb-structured Rh/Al2O3 coated catalyst. The transport of mass, momentum, energy and species in a reforming reactor are simultaneously solved using a three dimensional fully implicit unstructured finite volume approach. The nonlinear system of equations is solved by Newton’s method. Eight gas-phase species (CH4, CO2, H2O, N2, O2, CO, OH and H2) are considered for the simulation. The surface chemistry is modeled by detailed reaction mechanisms including 38 heterogeneous reactions with 20 surface-adsorbed species for rhodium catalyst and solved using the mean-field approximation model to obtain the surface convergence and reaction rates. The numerical results are compared with the experimental data and good agreement is observed. The simulation is performed for a reforming reactor with a channel density of 600 cpsi (channels per square inch). The governing equations for fluid and solid regions of the monolith are simultaneously solved with considering the catalytic combustion at their interface. The performance of the reforming reactor is numerically studied. A finite element approach is used to obtain the thermal stresses based on the temperature field obtained from the solid/fluid FVM solver.