A numerical method is presented for the two dimensional quasi steady state heat transfer on high power density laser welding processes according to the keyhole model.The mathematic model is estabilished on the basis of the conservation of mass,momentum and energy.Computation has been performed in the curvilinear coordinate system by using the finite volume method.A position predict correct procedure was developed to accurately identify the solid liquid interface location during welding.Numerical example is on the study of a typical keyhold welding process of an AISI304 Stainless Steel plate.