The　fracture　behavior　of　air　plasma-sprayed　8%　yttria-stabilized　zirconia　(8YSZ)　thermal　barrier　coatings　was　characterized　by　analyzing　acoustic　emission　(AE)　signals　during　a　four-point　bending　(4PB)　experiment.　Characteristic　parameters　analysis,　cluster　and　wavelet　packet　transform　combining　with　micromorphology　and　stress　analysis　of　TBCs　were　used　to　obtain　the　failure　types　of　TBCs.　The　results　show　that　there　are　both　four　failure　types　under　the　two　loading　models.　Macroscopic　fracture　and　spallation　signals　have　no　obvious　frequency　band.　However,　the　dominant　frequency　bands　of　deformation　of　substrate,　surface　vertical　cracks,　opening　interface　cracks　and　sliding　interface　cracks　signals　can　be　distinguished　clearly　at　0-156.25　kHz,　156.25-234.375　kHz,　312.625-390.625　kHz,　and　390.625-468.75　kHz,　respectively.　As　for　the　outer　bending,　surface　vertical　cracks　appear　continuously　and　then　transform　into　opening　interface　cracks　at　the　interface　of　bond　coat　and　ceramics　top　coat.　As　for　the　inner　bending,　however,　sliding　interface　cracks　appear　near　the　interface　of　bond　coat　and　ceramics　top　coat,　presenting　only　small　number　of　surface　vertical　cracks.　Both　kinds　of　interface　cracks　can　cause　macroscopic　cracks　and　spallation　of　thermal　barrier　coatings.　©　2019,　Editorial　Office　of　CHINA　SURFACE　ENGINEERING.　All　right　reserved.