The flow dynamic behaviors and characteristics of a two-stage viscous pump with two rotating cylinderes in microchannels were numerically studied by laminar model. At low Reynolds numbers, the dimensionless mass flow rate almost keeps constant for similar flow structure in the identical type of pump, and it also has little variation with different types of pump expect for the staggered pump with very small distance between different cylinders. As the Reynolds number increasing, the dimensionless mass flow rate drops because of the vortices evolution, and the distance between different cylinders significantly affects the flow dynamic process. For large distance, two steady vortices appear behind the cylinders, and the flow dynamics of aligned and staggered pump are very similar. For small distance, the flow rate of the staggered pump almost decreases with the distance rising, while the flow rate of the aligned pump has a maximum at a specific distance. Corresponding to the single-stage pump, the mass flow rate of two-stage pump is remarkably enhanced, and the enhanment ratio will increase as Reynolds number droping. Meanwhile, the driving power of two cylinders drops very slowly as the distance decreasing.

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