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The evolution of metal flow, microstructure and corrosion properties of 5A06 alloy after friction stir welding has been studied in present paper. It was observed that metal on the advancing side is curled directly into the threads and then is extruded down into the weld nugget zone by complex motions of torsion and swirl. However, the material on the retreating side encounters chaotic flow patterns. The electro backscattering diffraction results indicated that the grains in stir zone were pronouncedly refined by dynamic recrystallization, the average grain size is about 6μm. The scanning electron microscope analysis displayed that β-phase (Al₃Mg₂) and Al₆(Mn, Fe) dispersedly distribute in the stir zone and the size of the Al₆(Mn, Fe) is smaller than that in base material. The hardness profile is characterized by material softening along the cross-section and the minimum hardness value of 72HV is located in the interface between stirring zone and thermo-mechanically affected zone. It was evident that the stir zone exhibits better corrosion resistance than the base material. The corrosion potential of stir zone is 35mV larger than that in base material (-0.725V).