This paper proposes a systematic procedure for designing a microreactor with slit-type mixing structure. The proposed approach enables us to effortlessly determine the design parameters of the microreactor that can achieve the perfect mixing in the desired residence time. The Fourier number is built into the proposed method to avoid repeating CFD simulation. Furthermore, an index that estimates the difference between the reaction yield calculated by using PFR model and that provided by CFD simulation is proposed. The dependence on CFD simulation can be reduced through the introduction of this index. The combination of the above-mentioned approaches promotes the efficiency in microreactor design. The validity of the proposed design procedure is assessed through a case study. © 2006 Elsevier B.V. All rights reserved.