**Abstract**

In microchannel, fluid viscous effect becomes dominant, and the micro-flow typically falls in laminar regime. Mixing of fluid in the absence of turbulence is a slow molecular process as it is solely dependent on diffusion. Fast and complete mixing of relevant fluids is of crucial importance in many chemical engineering processes, thus computational fluid dynamics simulation on mixing in microchannel is the main topic in this chapter. The simulation was based on laminar flow and convective diffusion equation model. The factors affecting the mixing performance in microchannel was further simulated. The finding provides some insight of transport phenomena on mixing in microchannel.

**Keywords:** mixing, microchannel, laminar, diffusion, simulation
