Filler materials, shielding gas and welding parameters influence MAG welding process, welding joint and its chemical composition and structure of high-strength steel. In this research the influence of four different shielding gases on MAG welding process of high-strength low-alloyed steel (650 MPa) in spray-arc conditions is carried out. As welding parameters increased and CO2 content was decreased in shielding gas, plasma had much more influence than the short current in the welding pool. Oxygen mixture is not suitable for high-parameter welding of high-strength steel.