A numerical method is presented for analysing 2-dimensional quasi-steady state heat transfer in high power density laser keyhole welding processes. The mathematical model is established according to the conservation of mass, momentum and energy. Computation is performed by using the finite control-volume method in the curvilinear coordinate system. A position prediction-correction procedure is employed to identify the solid-liquid interface location. This method is applied to the study of a typical keyhole welding process of an AISI 304 stainless steel plate and its feasibility is verified.