Objective To investigate growth kinetics of TBCs and pure BC as well as microstructure evolution of TGO in TBCs. Methods Variations in TGO thickness of APS-TBCs and pure BCs after isothermal oxidation at 1100 ℃ for 2,5,10,20,50,100, 200,350 h were comparatively analyzed. XRD and SEM were used to characterize the surface and cross-section of TBCs. Results TGO growth kinetics for both samples followed parabolic laws, and the oxidation rate constants of TBCs and pure BC were 0. 344 μm/ h0. 5 and 0. 354 μm/ h0. 5, respectively. TGO mainly consisted of α-Al2O3 after isothermal oxidation for 5 h. CoO, NiO, Cr2O3 and spinel oxides appeared with the increase of oxidation time. CoO disappeared, and content of NiO reduced while contents of Cr2O3 and spinel oxides increased after isothermal oxidation for 100 h. Cracks appeared but failure of TBCs did not occur after isothermal oxidation at 1100 ℃ for 350 h. TGO eventually consisted of a sub-Al2O3 layer with columnar microstructure and the upper porous mixture. Conclusion TCs had little effect on the oxidation rate constant of BCs. α-Al2 O3 was firstly formed in TGO and grew in form of columnar crystals, then mixed oxides appeared on α-Al2 O3 and the growth rate of TGO became slow.