Abstract: Experimental study on friction stir welding of AZ31B magnesium/6061 aluminum alloy under different welding processes was carried out. The microstructure of the welded joints was observed using optical microscopy（OM） and scanning electron microscopy（SEM）, and the mechanical properties of the joints were characterized by tensile test and Vickers hardness test. The results reveal that the weld nugget zone exhibits strip-like structures composed of Mg₁₇Al₁₂and Mg₂ Al₃. With the increase of the rotational speed of the stirring tool, the grains of the weld nugget zone are refined, the average hardness value increases. With the increase of the welding speed, the number of unbroken magnesium alloy blocks in the weld nugget zone has gradually increased, and the average microhardness of the weld nugget zone gradually decreases.With the increase of the rotational speed of the stirring tool or the welding speed, the tensile strength of the joints firstly increases and then decreases. The joint has the highest tensile strength of 168 MPa, when the rotational speed is 1000 r/min and the welding speed is 30 mm/min.