This　paper　presents　a　thorough　study　on　plasma　sprayed　8　wt%　Y2O3-stabilized　ZrO2　(8YSZ)　thermal　barrier　coatings　intended　to　show　the　effect　of　the　internal　microstructure　especially　the　pores　on　mechanical　properties　of　plasma　sprayed　coatings.　The　internal　microstructure　of　8YSZ　thermal　barrier　coatings　was　analyzed　comprehensively　by　image　processing　technology　combined　with　fractal　theory.　The　mechanical　properties　of　8YSZ　coatings　were　tested　by　the　instrumented　indentation　testing.　And　the　stress　distribution　in　three　models　with　different　microstructure　of　coatings　was　analyzed　in　depth　by　the　finite　element　method.　It　was　found　that　plasma　sprayed　8YSZ　thermal　barrier　coatings　have　a　typical　layered　structure　and　contain　many　microscopic　defects　such　as　microcracks　and　pores.　The　pore　size　distribution　of　plasma　sprayed　8YSZ　coatings　obey　the　logarithmic　normal　distribution,　and　the　pore　diameter　inside　the　coating　is　mainly　concentrated　between　1　and　10　µm.　With　the　increase　of　high　temperature　thermal　exposure　time,　the　average　diameter　of　pores　gradually　decreased　from　9.30　µm　to　5.96　µm,　and　the　porosity　of　the　ceramic　top　coat　is　reduced　from　9.38%　to　5.79%.　Fractal　characterization　results　showed　that　after　a　certain　period　of　thermal　exposure,　the　ceramic　top　coat　become　densified,　and　the　internal　pore　structure　is　regularized　with　the　fractal　dimension　decreased　from　the　initial　value　of　D1　=　1.26　to　the　D6　=　1.12　after　200　h.　The　indentation　testing　results　showed　that　after　200　h　of　high　temperature　thermal　exposure,　the　hardness　of　8YSZ　coatings　increased　from　2.52　GPa　to　3.12　GPa,　and　the　elastic　modulus　increased　from　32.3　GPa　to　43.6　GPa.　The　results　of　finite　element　analysis　showed　that　the　complex　pore　structure　inside　the　coating　will　lead　to　stress　concentration,　which　were　largely　affects　the　mechanical　properties　of　8YSZ　coatings.　©　2018　Elsevier　Ltd　and　Techna　Group　S.r.l.