The alloys with Sc content of 0 and 4 wt.% were prepared by vacuum hot press sintering using elemental Sc powder and Fe-21Cr-4Al pre-alloy powder as raw materials. The element Sc changed the XRD phases of Fe-21Cr-4Al alloy. In addition to the original matrix α-Fe phase, three Sc-rich phases are formed, namely, ScAlO₃, Sc₂O₃ and Sc elemental. Meanwhile, Sc addition resulted in the formation of a protective corrosion product film on the corrosion face of alloy, which limited corrosion ion diffusion, thus reducing the corrosion rate of the alloy and enhancing its corrosion resistance. However, due to the lack of protective corrosion product film on the surface of alloys without Sc, large corrosion pits appear on the corrosion surface, and these pits continue to expand under the continuous erosion of corrosion ions. The corrosion speed of the alloy with Sc added was 4.302 mm/y, which was about 48.34% lower than that of the alloy without Sc.