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The release of hazardous gas increases with the development of industry. The research of gas-sensitive materials has attracted attention. Nanoscale iron oxide (α-Fe₂O₃) is one of the research hotspots of gas-sensitive materials because it is a cheap, non-toxic semiconductor material. In this study, pomegranate-shaped α-Fe₂O₃ was synthesized using an in situ corrosion method of scorodite. Spherical-shaped α-Fe₂O₃ nanoparticles were included in the octahedral shells. The forming process of the structure was analyzed by a variety of measurements. The shell was formed first through the deposition of Fe(OH)₃, which was produced by hydrolyzing scorodite. Then, the corrosion was continued and Fe(OH)₃ precipitation was produced below the shell. The particles aggregated and formed spheres. The pomegranate-shaped α-Fe₂O₃ was formed when the scorodite was hydrolyzed completely. The gas-sensing properties of α-Fe₂O₃ were investigated. The results showed that pomegranate-shaped α-Fe₂O₃ was responsive to a variety of gases, especially xylene. The value of R_a/R_g was 67.29 at 340 °C when the concentration of xylene was 1000 ppm. This indicated the pomegranate-shaped α-Fe₂O₃ has potential application as a xylene gas sensor.