The multiscale modeling of a reaction-transport process is an important issue in both fundamental and applied studies. We introduced a reaction−diffusion−convection model to deal with the reaction-transport process in chemical engineering by combining the reaction kinetics model, classical density functional theory (CDFT), and computational fluid dynamics (CFD). The reaction kinetic model and CDFT are unified into a differential equation, which is coupled with the CFD equation by a boundary condition. The model is applied to NO oxidation in a reactor. The multiscale model reveals the relationship between the microscopic properties and the macroscopic performance of a catalyst/reactor. We examined the dependence of conversion on adsorption strength, the shape and number of catalyst particles, and flow velocity. The multiscale prediction is consistent with the experiment, and there is a selfinhibition effect in the reaction-transport process. The model gives some insight into the design of reactors and has the potential to be applied to other reaction-transport processes.