Abstract: Friction stir spot welding (FSSW) is a relatively new solid state joining method, which is a variant of friction stir welding.The effect of the welding parameters on the shaping and mechanical properties of friction stir spot welded joint of 2 mm LY12 Al alloy was investigated.The results show that, when the welding time is fixed, welding spot appearamce is better with the increasing of the tool rotation speed, and it becomes worse with the decrease of the tool rotation speed and the welding time.The tensile shear strength of the spot increases firstly, and then reduces with the increasing of tool rotation speed.When the tool rotation speed is 950 r/min and welding time is 12 s, the maximum strength is up to 9.33 kN/spot.The microhardness show that the distribution of microhardness is high-low-sight higher-low-high along the centre of the keyhole, and the minimum value is in the heat affected zone, and the microhardness of plasticity zone was slightly lower than that of base metal.