Abstract: Annealed Al-coating 7B04 Al sheets in thickness of 2 mm are subjected to friction stir lap welding (FSLW). The effect of alclad cladding, welding parameters and heat treatment on the quality, microstructure and mechanical properties of the FSLW joints are investigated. The results show that the original alclad layers can not be completely broken up and dispersed into the nugget zone. The dispersion of the alclad layers in the advancing side is quite obvious, however this is not the case in the retreating side, which is basically maintained as the original state. The pore defect in the nugget zone can be effectively eliminated by increasing the rotation rate and the shoulder size. The tensile strength of the FSLW joint increases with increasing the rotation rate or the shoulder size. The effect of the alclad layer does not show apparent effect on the tensile strength of the welded FSLW joints, and the strength of the joints is about 94% of that of the base material; however, this effect is obvious for quenched joints, the joint strength is only 64% of that of the quenched base material.