Abstract: This paper described the flow,heat and mass transfer, and heterogeneous catalytic reaction in three-way catalytic converter, analyzed the correction of the radial heat conductivity, and compared the diffusion coefficients when the exhaust gas was considered as a binary and multicomponent mixture respectively.A two-dimensional symmetrical transient model applicable to cold-start emission applications was integrated, which was solved by the finite volume method.The model can be used to simulate and explain effects of the flow and temperature distribution on the performance of the converter.Computational results and their analyses were described in the paper Ⅱ.