NiCrCoAlY particles and coatings were prepared by plasma spraying technique. The oxidation behavior of NiCrCoAlY particles in the plasma spraying process and the influence of shrouding gas on high-temperature oxidation resistance of NiCrCoAlY coatings were investigated. The results show that there are two oxidation mechanisms during in-flight oxidation. One is convective oxidation, and the other is diffusion oxidation. In the plasma?zone whose distance to the nozzle is less than 55 mm, convective oxidation is the dominating oxidation mechanism; in the zone whose distance to the nozzle is?more than 55 mm, diffusion oxidation is the principal mechanism. Besides the in-flight oxidation, the oxidation after spraying also occurs for the particles. In-flight oxidation is the main oxidation mechanism for NiCrCoAlY particles in plasma spraying. Shrouding gas can decrease the oxide content of in-flight oxidation and increase the oxidation resistance of NiCrCoAlY coatings