Abstract: By plating Ni and Ni/Cu as composite transitional layer and using zinc as filler metal, industrial pure aluminium and low carbon steel were joined by friction stir brazing(FSB) technique. The shear test and peel test of the joint were carried out and were compared with joints with out transitional layer. The microstructure of joints were preliminarily analyzed by using scanning electron microscope and energy spectrum analysis. The effect of transitional layer to the mechanical property and microstructure of the aluminum-steel FSB joint was studied. The results show that the failure load of the joint peel test was increased and the mechanical performance was improved to some extent when adding transitional layer to the interface, the Al-Fe intermetallics were barely generated in the center region of the joint interface.