The automotive industry and emission system suppliers invest considerable efforts for the improvement of the conversion efficiency of a catalytic converter, in order to lower vehicle emission. One of the methods to improve the catalyst conversion efficiency is to use a higher cell density brick with a thinner wall to increase its geometric surface area. However, there is a significant drawback for the system - higher pressure loss along the brick. Moreover, the mechanical strength and thermal degradation of the brick become major concerns. In this paper, the concept of a brick with radially variable cell density is introduced to possibly resolve several issues. A CFD study was conducted to verify benefits in both flow efficiency and pressure loss along the brick with several different flow rates. The results show that with the variable cell density brick, the flow uniformity improves with different flow rates and prevents the flow from concentrating in one specific area, which may contribute to extend catalyst life. Also, pressure loss along the brick are reduced 7% to 15%, compared to those with uniform cell density.