The　effects　of　an　internal　nonlinear　energy　sink　(NES)　on　a　truss　core　sandwich　plate　in　dynamics　are　investigated.　The　energy　dissipation　of　the　NES　is　studied　with　the　sandwich　plate　excited　by　a　half-wave　shock.　It　is　found　that　exceptional　vibration　absorption　is　achieved　by　the　NES.　Moreover,　the　relative　motion　between　the　sandwich　plate　and　the　NES　remains　in　the　acceptable　range　of　the　hollow　truss　core　until　the　shock　amplitude　becomes　too　large.　The　slow　flow　equation　and　the　frequency　response　of　the　system　are　obtained　by　employing　the　complexification-averaging　method.　Although　the　NES　exhibits　excellent　performance　when　the　sandwich　plate　is　under　an　excitation　with　a　relatively　small　amplitude,　the　efficiency　is　gradually　diminished　with　the　emergence　of　a　stable　higher　branch　and　the　merging　of　higher　and　lower　branches.　During　the　entire　process,　the　NES　does　not　collide　with　the　face　sheet　of　the　sandwich　plate.　Further,　the　variation　of　vibration　absorption　performance　of　the　NES　with　the　increase　of　strut　radius　is　investigated.　It　is　demonstrated　that　the　variation　of　the　strut　radius　has　a　greater　influence　on　the　vibration　absorption　with　a　harmonic　load　in　comparison　to　absorption　with　a　shock　load.