For redox flow batteries, the reaction distribution in macro or device-scale has been studied, however the reaction distribution in pore-scale is not well understood. Moreover, the understanding on how the reaction distribution in pore-scale impact the overall flow battery performance is lacking. This study introduces a framework that can provide the multi-scale path that help researchers understand the relationship between pore-scale electrode structure reaction and the device-scale electrochemical reaction uniformity for the redox flow batteries. A reduced model is build based on the 128 pore-scale simulations, which provide a quantitative relationship between the battery operation conditions (inlet velocity, current density, inlet concentration) and the surface reaction uniformity for the pore-scale sample. The multi-scale framework upscale the pore-scale surface reaction uniformity to device-scale combine uniformity. The inlet velocity can be optimized based on this multi-scale framework, and a time-varying inlet velocity can be derived for an example flow battery setup. It shows that keeping a constant inlet flow rate for the entire charging period waste much pump power comparing to the optimized time-vary inlet flow rate. Figure 1 shows the optimized flow rate and inlet concentration evolution with color lines represent various flow rate for different target normalized standard deviation of surface reaction rate.