Abstract: The preheating temperature and cold crack sensitivity of low alloy high strength steel JFE980S were calculated according to the empirical formula and the measured diffusible hydrogen content.By the Y-slit type cracking test,the metallographic test,and the residual stresses measurement,the cold crack resistance of the low alloy high strength steel joint were analyzed and compared between the laser-arc hybrid welding and the MAG welding.The results show that the steel welded by laser-arc hybrid welding has smaller cold crack tendency than that by the MAG welding because of the higher weld penetration and the decreases in the welding stress.The laser can preheat the base metal when the laser is ahead of the MAG arc,and the steel has lower welding residual stresses.Laser-arc hybrid welding has an advantage over the MAG welding without non-preheating welding for JFE980S high strength steel.