In　modern　gas　turbine,　the　over　tip　leakage　flow　is　inevitably　generated　in　the　tip　gap　of　the　first　stage　turbine　blade　due　to　the　freestanding　airfoil.　In　order　to　obtain　a　higher　thermal　efficiency,　the　turbine　inlet　temperature　is　gradually　increased.　Therefore,　the　over　tip　leakage　flow　induces　significant　aerodynamic　losses　and　the　blade　tip　and　the　over　tip　casing　endure　high　level　of　thermal　load.　In　the　pursuit　of　a　high-performance　turbine　engine,　cavity　tips　are　widely　implemented　in　the　turbine　blade　to　reduce　the　over　tip　leakage　flow　and　the　thermal　load　on　the　blade　tip　and　over　tip　casing.　In　the　current　study,　the　influences　of　the　multi-cavity　squealer　tip　on　the　blade　tip　and　the　over　tip　casing　aerothermal　performance　were　numerically　investigated.　Three-dimensional　(3D)　Reynolds-Averaged　Navier-Stokes　(RANS)　equations　and　standard　k-ω　turbulence　model　were　solved　to　conduct　the　simulations.　The　results　indicate　that　the　flat　tip　attains　the　largest　thermal　load　on　the　blade　tip,　over-tip　casing　and　induces　the　largest　total　pressure　loss.　However,　the　case　with　a　single　tip　cavity　(1CST)　achieves　the　smallest　total　pressure　loss　and　heat　transfer　coefficient　on　the　over-tip　casing,　which　are　7.6%　and　19.6%　lower　than　the　flat　tip,　respectively.　The　case　with　a　multi-cavity　tip　obtains　a　decreasing　heat　transfer　coefficient　on　the　blade　tip.　The　case　with　five　tip　cavities　(5CST)　achieves　the　smallest　heat　transfer　coefficient　on　the　blade　tip　among　all　simulated　cases,　which　is　decreased　by　17.5%　relative　to　the　flat　tip.　©　2018　Elsevier　Ltd