Abstract: 30CrMnSiA steel plates with a thickness of 2 mm were welded by CO₂ Gas Metal Arc Welding (GMAW) with infrared heating during welding. The influences of the infrared heating process parameters on mechanical properties and microstructure of welds have been investigated, and mechanical property of the welds was analyzed. The results shown that, the completely quenched zone was constituted with lamellar martensites. The lamellar martensites which in the completely quench zone has descended when using infrared device after welding, when the distance between troch and infrared is 250mm,the highest hardness in joint is 511.1 HV which is lower than 675.2 HV that welded without use infrared after welding. The mechanical properties of the joint are significantly improved when using infrared device. The tensile strength at this condition is 950MPa which is higher than 890MPa at generally welding condition. And the completely quenched zone is no longer the weakest zone of the joint.