Abstract: Based on the specific laserwelding process of aluminum alloy, two kinds of heat sources were used in this calculation which could reflect effect of laser plasma and laser beam during laser welding process.The formation and development of keyhole has been analyzed by FEM and the calculation has coincidence with the result of laser welding experiment.The model is reasonable and welding seams can be predicted, by this model thus it helps to choose appropriate parameters for laser welding of aluminum alloy.It makes the laser welding of aluminum alloy more conveniently used in the industry.