Using in low temperatures causes embrittlement of many structures, consequently, selection of welding parameters for maintaining the toughness of welded structures, is so important. In this paper, effects of arc heat input and welding speed on the cryogenic impact strength of type 304L austenitic stainless steel weld metal, are investigated. For this purpose, 304L austenitic stainless steel sheet with 5 mm thickness, was welded with gas tungsten arc welding process and by changing the parameters of arc heat input and welding speed, the effect of these parameters on the microstructure, the weld metal ferrite content and low temperature charpy impact energy of samples, was determined. The arc heat input range applied was between 1.04 and 3.23 kW, and the welding speed varied between 30 and 240 mm/min. It was found that, increasing of arc heat input can reduce weld metal ferrite content, which improves low temperature impact strength, but on the other hand, slow cooling due to increasing heat input results in coarser dendritic structures in the weld metal, and can adversely affect on impact strength. Changes of Welding speed can also affect on the amount of ferrite and microstructure and thus have influence on the impact strength. Finally having carried out the numerous tests, optimum impact properties at low temperature, were obtained at 1.67 kW arc heat input and 120 mm/min welding speed.