A comprehensive two-dimensional (2D) reactor model has been developed to simulate the reaction performance in a packed bed reactor for producing ethylene oxide. An exponent-function kinetic model has been incorporated to a commercial computational fluid dynamics (CFD) code FLUENT by user defined functions for the reaction performance modeling for ethylene expoxidation. The approach and model have been validated with the actual data collected from research papers where the same kinetic model is adopted. Various graphs indicating the variation of pressure, temperature and velocity along the packed bed reactor are given. Temperature, inlet ethylene and oxygen concentrations are important factors for ethylene oxide selectivity. It is demonstrated that regulating the concentrations of ethylene and oxygen, leads to high selectivity of ethylene oxide. When the ethylene concentration is maintained at 25.6%, it was noticed an increase in ethylene oxide selectivity with increasing concentration of oxygen. At high ethylene concentrations between 10 and 25.6%, higher selectivity to ethylene oxide is obtained. The temperature has a significant function in increasing ethylene oxide selectivity in the packed bed reactor; high reaction temperature up to 503 K promotes high selectivity to ethylene oxide as well as higher conversion of ethylene and oxygen. The optimal temperature is between:463-503 K. The mole fractions of ethylene oxide and carbon dioxide increases with the increase in reaction temperature. At 503 K the concentrations of oxygen, methane and ethylene decreases while the concentrations of ethylene oxide, water and carbon dioxide increased. To summarize, the simulation results show that the ethylene oxide selectivity and the concentrations of oxygen and ethylene are closely related to each other and are obviously influenced by operating conditions studied in this work.