Laser spot welding of aluminum alloy is difficult for its high optical reflection and thermal conductivity. The quality of the spot weld depends strongly on the condition of material surface. In this paper laser spot welding of aluminum alloy with different laser pulse shapes was carried out, and the relationship between the pulse shape and the quality of laser spot welds was investigated. Due to the high reflection of aluminum alloy the enhanced spike pulse shape, which has an initial spike of 1.8 kW laser power was used. The surface metal vaporized and keyhole formed, so the rest of laser power can be absorbed sufficiently. The results show that the repetition of laser spot weld was much better using this enhanced spike pulse shape. The ramp-up pulse shape can help to exclude the surface oxide film and stable the formation of spot weld. In addition, cool-down pulse shape was used to minimize the defects such as crack and porosity in the weld. However the surface crater of spot weld using cool-down pulse shape was obviously deeper than the rectangular pulse shape. At last, saw-like pulse shape, which combine the advantages of cool-down and ramp-up pulse shapes, was used and the quality of spot weld was excellent.