Abstract: Preparing a reasonably structured oxide film on the surface of the alloy steel piercing plug is of great significance for extending service life thereof. In order to identify the effect of relevant alloying elements on formation of the oxide film，high-temperature oxidation of the 10Mn，15CrNiMoW2，and 316L plugs is carried out at 1 020 ℃ in the atmosphere of drop-feeding of the mixed C₂H₅OH-H₂O solution. The oxidation behavior is characterized by means of using the SEM，the XRD，the EDS，the OM，and the microhardness tester. It is revealed via the research that the W promotes the growth of spinel phase of the oxide scale，increases the spacing of the crystal planes，and intensifies the internal oxi- dation of the metal matrix. The results show that as the contents of Ni and Cr increase，the distribution of relevant eleme- nts presents different morphological characteristics. The formation of Ni-enriched walls and Cr-enriched oxide walls in the 316L plug steel significantly hinder the diffusion of O₂^- from the external oxide layer to the internal one so as effectively get the oxidation resistance of the steel improved.