The　formation　of　thermally　grown　oxide　(TGO)　during　high　temperature　is　a　key　factor　to　the　degradation　of　thermal　barrier　coatings　(TBCs)　applied　on　hot　section　components.　In　the　present　study　both　the　CoNiCrAlY　bond　coat　and　ZrO2-8　wt.%　Y2O3　(8YSZ)　ceramic　coat　of　TBCs　were　prepared　by　air　plasma　spraying　(APS).　The　composition　and　microstructure　of　TGO　in　TBCs　were　investigated　using　scanning　electron　microscopy　(SEM),　energy　dispersive　spectroscopy　(EDS)　and　X-ray　diffraction　(XRD)　analysis.　The　growth　rate　of　TGO　for　TBC　and　pure　BC　were　gained　after　isothermal　oxidation　at　1100　°C　for　various　times.　The　results　showed　that　as-sprayed　bond　coat　consisted　of　β　and　γ/γ＇phases,　β　phase　reducesd　as　the　oxidation　time　increased.　The　TGO　comprised　α-Al2O3　formed　in　the　first　2　h.　CoO,　NiO,　Cr2O3　and　spinel　oxides　appeared　after　20　h　of　oxidation.　Contents　of　CoO　and　NiO　reduced　while　that　of　Cr2O3　and　spinel　oxides　increased　in　the　later　oxidation　stage.　The　TGO　eventually　consisted　of　a　sub-Al2O3　layer　with　columnar　microstructure　and　the　upper　porous　CS　clusters.　The　TGO　growth　kinetics　for　two　kinds　of　samples　followed　parabolic　laws,　with　oxidation　rate　constant　of　0.344　μm/h0.5　for　TBCs　and　0.354　μm/h0.5　for　pure　BCs.　©　2016　The　Authors.