Reactive plasma spray (RPS) technique is frequently used to prepare high-performance coating materials with different application requirements. Based on the classical thermite reaction, the Al-Fe₂O₃ coatings were fabricated by RPS under atmosphere and low-pressure ambient. The phase compositions and microstructures of the obtained coatings were characterized by XRD, SEM and EDS. Moreover, the reaction mechanisms of thermite reaction of Al and Fe₂O₃ in sintering and RPS process were elucidated. The DTA analysis results indicate that the main sintering products are Fe, Al₂O₃ and FeAl phases under prolongated reaction condition with Ar gas protetion. However, low oxygen partial pressure leads to the formation of FeAl₂O₄ hercynite phase as an intermediate product during spraying. In atmosphere-reactive plasma spraying (A-RPS), such phase can be retained in the final coating under extremely fast cooling rate. Furthermore, it can also be continuously reduced to FeAl phase in the low pressure Ar-H₂ ambience due to the deoxidation effect and long in-flight distance of plasma jet.