The aims is to study the effect of Si on the high temperature oxidation resistance of Fe-18wt.%Cr-3wt.%B alloy and develop a new type oxidation-resistant roll material. Fe-Cr-B directional solidification alloys with Si content of 0.0wt.%, 1.0wt.%, 2.0wt.%, and 3.0wt.% were prepared by directional solidification technology and the oxidation kinetics of the alloys were characterized by the weight gain method. Analyze the surface and cross-sectional morphology, structure and phase composition of the oriented alloy oxide film by means of SEM, XRD and other means and evaluate the effect of Si on the oxidation resistance of the oriented alloy. The addition of Si significantly refines the structure of the directionally solidified Fe-Cr-B alloy, which is beneficial to the directional growth of the hard phase M2B boride in the alloy. The oxidation results show that the addition of Si can reduce the oxidation rate of the alloy from 0.052 28 g/(m2.h) to 0.009 28 g/(m2.h) after being oxidized at 800 ℃ for 100 h, and the oxidation resistance is increased by more than 5 times. The addition of Si makes the surface oxide film of the oriented alloy smooth, compact and continuous without cracking and peeling. The analysis of the surface film structure shows that the oriented alloy oxide film is composed of Cr2O3, FeCr2O4, Fe3O4 spinel and the outermost Fe2O3 composite oxide from the alloy matrix to the surface. The addition of Si promotes the formation of the innermost SiO2 oxide film. The layer is in a continuous tortuous form at the interface between the oriented alloy and Cr2O3. At the same time, the oriented M2B hard phase and the internal oxide layer SiO2 in the oriented alloy present an “embedded” intercalation interface, which changes the interface bonding morphology and internal interface structure, and significantly improves the adhesion between the composite oxide film and the oriented alloy interface force. The failure of relatively coarse primary borides in the oxidation process of oriented alloys is mainly caused by the spalling of primary borides and the internal diffusion of oxygen inducing M2B cracking. Si significantly improves the oxidation resistance of the oriented Fe-Cr-B alloy. The main mechanism is that Si promotes the formation of the internal oxide layer SiO2 and leads to the production of the "inter-embedded" SiO2/M2B bidirectional intercalation structure. This film/alloy interface which is composed by “oriented inter-embedded pinned film structure” can effectively improve the adhesion of the film/matrix interface.