A experimental welding rod was made and welding tests were performed for the purpose of welding the spheroidal graphite cast iron at low preheat condition. AI, Bi, Ca, REM were added to the 3.9%C, 3.8%Si iron, and poured into the Cu mould to measure degree of chill by hardness, and determined the amount of each elements to be add avoiding serious chill for the experimental welding rod. It was performed a bead test on plate, repair welding test and a V groove welding for mechanical test by TIG welding using experimental welding rod. No crack was detected in the bead test on plate specimens even on the preheat condition of 369K. Hard chill was detected in the final layer under as weld condition for the repair welding test specimens, but as the distance from the final layer increased, fine graphits were found to increase considerably. Ferrite and fine graphite were detected at 10mm distance from the final layer in weld metal. The microstructure of heat treated specimen was ferrite and fine graphite in all deposited metal. A good tensile strength and fatigue limit was obtained in the mechanical tests of weld joint. The same welding rod and procedure were applied to spheroidal graphite iron casting with a thickness of 75mm, and the results were satisfactory.