Environmental awareness is increasing day by day. People want to use environmental friendly products. Vehicles have become one of the essential tools of people. The use of less polluting vehicles has also been made mandatory by countries. In internal combustion engines, the highest level of air pollutant exhaust gas emissions occur while the engine is running in cold start conditions. In this study, a catalytic converter was examined with a commercial software using a one-dimensional model during cold start. The effects of parameters such as grid number, grid shape factor, number of channels are examined. As a result, it has been determined that the one-dimensional model can be accepted in accordance with the literature. It has also been shown that the number of channels in the catalytic converter are important.