The mixing effect is studied by comparing rotating and oscillating stirrers in the micro channel. The cases of Re=10 to 80 with various stirring speeds are considered to analysis the effect of Re and stirrer speed for the mixing. Under Re=20, the oscillating stirrer represents better mixing rate than the rotating stirrer up to the critical stirrer speed which has a maximum efficiency. Over Re=30, the results of oscillating and rotating stirrer show that the faster the stirrer speed, the higher the mixing effect within the concerned stirrer speed range and the oscillating stirrer keeps the higher mixing rate. It was found that the mixing effect is a function which has an optimum of the Reynolds number and the stirrer speed. The D2Q9 Lattice Boltzmann Method is used due to the merits of calculation for the unsteady flow with moving boundary.