An experiment system aimed to direct analyze liquid steel based on Laser-Induced Breakdown Spectroscopy has been built. A laboratory-scale induction furnace of 1 kg capacity is used to melt steel sample. The process of oxidization in the surface of liquid steel under atmospheric conditions is tested, and its influence to the results of analysis is discussed. Ar is used as inert gas to exclude the ambient air from the surface of liquid steel, and the changes of the intensity and RSD of elementals emission lines with the flow rate of Ar are detailed. The results of analysis show that the relative intensities of alloying elements line increase with the formation of oxidization in the surface of liquid steel, because the formation of oxide mixtures by most of alloying elements lead to a higher fractional concentration of these elementals on the sample surface. The result of direct analysis of liquid steel can be improved using Ar as inert gas with an appropriate flow rate.