Abstract: Cold metal transfer lap spot plug welding experiments of 6061 aluminum alloy used in the automobile body were carried out by using AlSi₅ filler metal. The effects of wire feeding rate, spot plug welding time and hole diameter in aluminum plate on welding spot diameter, nugget diameter and tensile load were investigated. The experimental results indicate that wire feeding rate mainly affects welding spot diameter. Spot plug welding time and hole diameter in aluminum plate have a significant effect on nugget diameter and tensile load. Tensile load of the joint primarily depends on the nugget diameter and increases with the increase of nugget diameter, but welding spot diameter has little effect on the tensile load. The joint belongs to the typical fusion welded joint. The weld metals are composed of α-Al solid solution and Al-Si eutectic phase. Tear results in fracture in tensile test of Al-Al spot plug welded joint.