Reactor modeling for the oxidative coupling of methane over Na2WO4/Mn/SiO2 catalyst was addressed in the present study. The catalyst loading part was designed to be thicker than the inlet and outlet parts to reduce the rates of side reactions in the gas phase, and the optimal aspect ratio (L to D ratio) for no pressure drop and minimum side reactions was determined in experimental studies. Experiments were also conducted under a variety of operating conditions such as gas hourly space velocity (GHSV), CH4/O2 ratio and reaction temperature, and partial least-squares model was applied to predict the performance of the reactor. The validity of the developed model was corroborated by the comparison with experimental data, and normalized parametric sensitivity analysis was carried out. Finally, the genetic algorithm (GA) was applied to determine the optimal conditions for maximum production of ethane and ethylene.