Abstract: Friction-stir welding was employed in the welding experiment of spray formed 7055 aluminium alloy plate with thickness of 4 mm.The influence of the rotating rate and the welding speed on the mechanical properties of the joint,micro-structure of the weld,and the fracture mode were analyzed.The results showed that good-looking,defectless welds could be obtained with proper welding parameters.The mechanical properties of the joints were related to the welding parameters.When the rotating rate was 1 000 r/min and the welding speed was 100 mm/min,the joints achieved good mechanical properties.The tension strengths of the joints reached 455 MP,and the fracture mode was ductile and brittle mixed.The welds consisted of three zones,among which the weld-nugget zone consisted of fine equiaxed grains.The minimum micro-hardness occurred on the advancing side,which indicated the advancing side is the weakness of the weld.