The final goal of this research is to establish a systematic design method of T-shaped microreactors (T-MRs) with secondary flow using a reduced-order model (ROM). In this paper, a ROM which combines computational fluid dynamics (CFD) model and multi-resolution lamellar model is developed. Multi-resolution lamellar model is constructed from the N kinds of lamellar models with different width of layers. In each lamellar model, thin multi-layers of two fluids are arrayed alternately at the entrance of the mixing channel to express the increased material interface, and the concentration profiles in the flow direction are estimated by a reaction diffusion simulation between thin layers under the assumption of plug flow. The developed ROM requires the minimum number of CFD pre-simulations to extract model parameters such as weighting coefficients for superimposing different lamellar models. The main findings are: 1) the complicated mass transport processes of T-MRs obtained by 3-D CFD model is well captured by the ROM of 2-D, which is constructed from multi-resolution lamellas, and 2) the computational time based on the ROM is shortened to one-third of that based on just CFD model. © 2009 Elsevier B.V. All rights reserved.