Abstract: An ultra-sonic pulse tungsten-inert-gas (TIG) welding power source based on new type IGBT topology was developed. 0Cr18Ni9Ti austenitic stainless steel workpieces were welded by ultra-sonic pulse TIG welding and conventional direct current TIG welding respectively. In order to study the difference between joints welded by different welding technology, these weld joints were analyzed by means of X-radial check-up, tensile strength and specific elongation detection, optical-microscope and scanning electron microscope. With the ultra-sonic pulse TIG welding technology pulse current frequency being increased, it can be found that grains will be refined and the width of the coarse grain zone will be narrowed, correspondingly, small equiaxed grains zone will be enlarged. By contrast with conventional direct current TIG welding technology, these joints introduced by 30kHz ultra-sonic pulse TIG welding technology, have more small equiaxed grains in weld joints core, which indicates grain refinement phenomenon is distinct. The tensile strength and the specific elongation of these joints welded by 30kHz ultra-sonic pulse TIG welding technology were improved respectively.