Interface　fracture　toughness　and　fracture　mechanisms　of　plasma-/sprayed　thermal　barrier　coatings　(TBCs)　were　investigated　by　interfacial　indentation　test　(IIT)　in　combination　with　acoustic　emission　(AE)　measurement.　Critical　load　and　AE　energy　were　employed　to　calculate　interface　fracture　toughness.　The　critical　point　at　which　crack　appears　at　the　interface　was　determined　by　the　IIT.　AE　signals　produced　during　total　indentation　test　not　only　are　used　to　investigate　the　interface　cracking　behavior　by　Fast　Fourier　Transform　(FFT)　and　wavelet　transforms　but　also　supply　the　mechanical　information.　The　result　shows　that　the　AE　signals　associated　with　coating　plastic　deformation　during　indentation　are　of　a　more　continuous　type　with　a　lower　characteristic　frequency　content　(30-60　kHz),　whereas　the　instantaneous　relaxation　associated　with　interface　crack　initiation　produces　burst　type　AE　signals　with　a　characteristic　frequency　in　the　range　70-200　kHz.　The　AE　signals　energy　is　concentrated　on　different　scales　for　the　coating　plastic　deformation,　interface　crack　initiation　and　interface　crack　propagation.　Interface　fracture　toughness　calculated　by　AE　energy　was　1.19　MPam1/2close　to　1.58　MPam1/2　calculated　by　critical　load.　It　indicates　that　the　acoustic　emission　energy　is　suitable　to　reflect　the　interface　fracture　toughness.　Copyright:　©　2016　Editorial　Board　of　CHINA　WELDING.