Abstract: Two-sidod friction stir welding (FSW) of a 5-mm-thiek plate of 1050-H24 aluminum alloy was performed. The relations of tensile properties and fracture locations of joints to welding parameters were examined. Experimental results showed that the initial bead welding parameters, final bead welding parameters, and their mutual welding directions have different effects on the tensile properties and fracture locations of the joints. The effect of initial bead welding parameters is much lower than that of final bead welding parameters. The same-direction-welded joints possess relatively high strength and fracture on the advancing side (AS) or retreating side (RS), while the opposite-direction-welded joints demonstrate relatively low strength and fracture only on the AS. The experimental study showed that a rotation speed of 1500 r/min, a welding speed of 400 mm/min and a same-direction welding process comprise an optimum combination for the tensile properties of the joints. An ultimate strength of the joints up to 78% of the base material is obtained.