Abstract: Deep penetration laser welding was performed at aluminum alloy LF3Y2 under hot and press condition.A heat source model, which comprises a gauss plane heat source on the top surface and a revolved gauss body heat source, was presented in this condition.Numerical simulation was adopted by the heat source model and ANSYS software.The results show that sufficient width and penetration of weld could be obtained under high speed welding operation and the isotherms looked like ellipse.The temperature gradient was correspondingly higher in the front of moving heat source than at the end.The cross-section morphology of simulation welded joint was almost in accordance with the results attained by experiments which confirmed the reasonableness of the model.