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.