The　trailing　edge　of　high　pressure　gas　turbine　blade　in　aeroengine　is　usually　designed　as　thin　as　possible　to　achieve　higher　aerodynamic　efficiency.　However,　as　the　inlet　temperature　of　modern　gas　turbine　is　continuously　increasing,　thermal　stress　in　a　thin　trailing　edge　will　become　much　significant,　resulting　in　possibilities　of　erosion　and　creep　problems.　To　find　a　balance　between　these　two　conflicting　goals,　one　method　is　the　use　of　pressure-side　cutback,　which　extends　into　the　coolant　slot　to　get　film　cooling　and　also　achieves　a　thin　trailing　edge.　Due　to　the　interactions　between　mainstream　and　coolant　flow,　film　cooling　effect　on　trailing　edge　cutback　is　significantly　affected　by　the　vortex　shedding　downstream　the　cooling　slot.　To　resolve　the　coherent　flow　structures　and　understand　their　role　on　film　cooling　effect　on　trailing-edge　cutback,　this　paper　implemented　a　Very　Large　Eddy　Simulation　(VLES)　model　into　the　solver　ANSYS　Fluent　with　user　defined　functions.　By　introducing　a　resolution　control　factor,　the　turbulence　viscosity　predicted　by　transient　SST　k-ω　model　was　corrected　and　the　VLES　computations　were　realized　in　the　whole　computational　region.　With　the　VLES　method,　film　cooling　effectiveness　distributions　on　trailing-edge　cutback　at　three　blowing　ratios　were　computed　and　compared　against　the　experimental　data.　The　coherent　unsteadiness　in　cutback　region　was　visualized　to　reveal　the　mixing　process　between　mainstream　and　coolant　flow.　The　numerical　accuracies　between　different　unsteady　prediction　methods,　i.e.　URANS　(Unsteady　Reynolds　Averaged　Navier-Stokes),　SAS　(Scale-Adaptive　Simulation),　DES　(Detached　Eddy　Simulation),　DDES　(Delayed-Detached　Eddy　Simulation),　SBES　(Stress-Blended　Eddy　Simulation),　and　VLES　were　compared　with　respect　to　the　resolutions　of　cooling　effect　and　vortex　shedding.　The　results　show　that　the　periodic　vortex　shedding　induced　by　the　interactions　between　mainstream　and　coolant　is　the　main　factor　that　affecting　the　cooling　performance　on　cutback.　VLES　method　has　a　comparable　accuracy　in　predicting　the　film　cooling　effect　on　trailing　edge　cutback　with　DDES　and　SBES　approaching.　In　the　detached　shear　layer,　VLES　method　exhibits　a　good　ability　to　resolve　coherent　unsteadiness　caused　by　vortex　shedding.　Compared　with　URANS　and　SAS　methods,　the　VLES　method　has　a　higher　accuracy　in　resolving　the　periodic　vortex　shedding　and　film　cooling　effectiveness　distributions,　especially　in　low　blowing　ratio　cases.　Copyright　©　2020　ASME.