Abstract: A new technique of PAW is presented on the basis of investigation on the features of welding heat source and the mechanical condition of the molten pool, This new technique is characterized by using a dual-cusp magnetic field to make the plasma are flat and welding along the major axis of the cross section of are. The most valuable advantage of this method lies in the allowance of increasing the metal thickness for dual-sided formation by a single pass. This paper introduces the experimental results of welding 16mm thick stainless steel by this method under a real production condition. The technological characteristics of this technique and the pattern of the weld formation as well as the influencs of different parameters are discussed. Because the holing ability of plasma, by adopting this method, can be strengthened by increasing the field current, it is unnecessary to make a substantial increase of welding current for increased metal thickness. As a result, the sizes of the pool and the keyhole are restricted, So it is much easier to maintain the liquid metal in mechanical equilibrium