Numerical simulations of laminar water-Al2O3 nanofluids flow phenomena and thermal behavior (velocity, normalized temperature profiles, poiseuille number, local and averageNusselt number and friction factor) through a rectangular micro-channel with two baffles have been studied with the variations of baffle height, volume fraction percentages and Re, which has a significant issue in engineering applications. The governing equations have been solved by SIMPLE algorithm and FLUENT software has been used to visualize the simulation results which demonstrate that variation. of volume fraction and baffle height resulted in a significant change in normalized temperature and velocity profiles along the center line.