Al0.5CrCoFeNi　high　entropy　alloy　was　prepared　by　vacuum　arc　melting　in　a　high-purity　argon　atmosphere.　The　oxidation　experiments　were　performed　at　the　temperatures　of　800,　900,　1000　and　1100℃　for　100　h,　and　the　corresponding　oxidation　kinetics　curves　have　been　tested.　The　structure　and　morphology　of　oxide　layer　have　been　studied　by　adopting　the　analytical　methods,　such　as　XRD　and　SEM.　The　results　show　that　oxide　films　forming　at　800℃　and　900℃　were　complete　and　compact,　and　have　excellent　oxidation　resistance.　However,　the　oxide　films　forming　at　1000℃　and　1100℃　become　much　thicker　and　have　a　large　number　of　cracks　and　holes,　which　result　into　poor　oxidation　resistance.　Interface　reactions　played　a　mast　role　at　the　early　stage　of　oxidation,　but　with　the　growing　of　oxide　films,　diffusion　process　played　an　important　role　increasingly,　and　became　the　control　factor　for　continue　oxidizing.　Then,　one　or　multiple　kinds　of　alloy　elements　oxide　precipitated　on　the　surface,　and　formed　inner　spinel　oxide　of　NiCr2O4,　CoCr2O4　and　Fe(Cr,Al)2O4.　During　the　high　temperature　oxidation　process,　N2　will　react　with　Al　to　generate　AlN　particles.　The　further　oxidizing　has　made　AlN　particles　oxidized　again　and　N2　escaped.　Finally,　the　holes　with　the　AlN　particles　shape　have　appeared.　Copyright　©　2015,　Northwest　Institute　for　Nonferrous　Metal　Research.　Published　by　Elsevier　BV.　All　rights　reserved.