Abstract: In case of carbon equivalent as 0.58%，the ASTM 1035 low-carbon steel is apt to have significant quench hardness which often leads to development of cracking during welding operation. Based on study of the mechanisms of the said cracking，proper welding process is prepared. The on-the-site operation with the process proves that the cracking severity can be remarkably reduced by means of a number of on-the-site process detail-control actions，including pre-heating prior to welding，selecting welding consumable containing low contents of C，S and P，and no or low content of nickel and having excellent toughness and well-matching strength，properly controlling the formation factor of the weld，reducing the dilution rate of the deposited metal，reducing the contents of C，S and P of the weld metal，using the small current and slow welding speed techniques，strictly controlling the welding heat input，determining proper pipe-end gap for joining，mounting arc run-on/off tab，temperature-keeping transport of the material during inner welding operation，and back gouging during tack welding，etc.