It is more complicated to weld Low Alloyed High-Strength steel materials than standard structural steel. Chemical composition of these materials makes the process harder as it is important to keep the high strength properties of the steel even after the process is done. An important influence in MAG (Metal Active Gas) welding of such steels makes the choice of welding wire, welding parameters and shielding gas composition. Appropriate choice of welding wire and shielding gas is an important issue in welding of Low Alloyed High-Strength steel. Change of welding parameters changes the heat input, type of welding wire transfer and the welding process in general. Shielding gas can influence the stability of welding parameters. The influence of shielding gas has been investigated for structural steels (till 275 – 355 MPa). There are also articles about very High strength steel (900 – 1000 MPa) MAG welding where the shielding gas influence on welding joint were carried out. As these investigations show that the influence of Argon mixture with 8% Carbon dioxide (CO2) is much better then mixtures with higher CO2 content authors have stated that the same influence can be on low alloyed High strength steel (550 – 650 MPa) MAG welding. High welding parameters can also influence the welding process. Lower heat input is an important issue in welding of High strength steels. Because of previously mentioned reasons the influence of 8% CO2 mixture in Argon on MAG welding of low alloyed High strength steel at high welding parameters was carried out in this investigation. Better results in combination of penetration + inclusions + hardness was reached with lower welding parameters.