A mathematical model of the flows in honeycomb monolith was established by an equivalent continuum approach, and the commercial code STAR-CD was utilized to simulate multi-dimensional steady turbulent room airflows in catalytic converters with different configurations. In order to verify the computing model, a pitot tube was used to measure the velocity distribution in the converter. Validations demonstrate that theoretical values agree well with experimental results.Simulation results show that, the larger the inlet cone angle the more the pressure loss and maldistribution in converters, however, when the angle enlarges enough its effect on flows will be obviously decreased thereafter. An enhanced diffusion header has benefits to the flow characteristics. Compared with the inlet cone angle, the outlet cone angle has little influences on the performance of flows. The spherical shape of the front face of monoliths proposed by authors is capable of improving the flow distribution. The monolith location has no significant effects on the flow quality. In addition, the larger the gap between two monoliths the more uniform the flow distribution for the second monolith but the less for the first. These results offer a practical guide to the optimum design of automotive catalytic converters.