In　this　study,　a　model　for　the　nonlinear　dynamic　analysis　of　the　geometrically　imperfect　sandwich　beam　with　functionally　graded　material　(FGM)　facets　and　auxetic　honeycomb　core　is　proposed.　The　auxetic　feature　of　the　honeycomb　material　is　realized　by　a　homogenization　method,　which　gives　the　expressions　of　the　effective　material　coefficients　in　terms　of　material　property　and　cellular　geometric　parameters.　The　nonlinear　motion　equation　of　the　geometrically　imperfect　beam　is　derived　based　on　the　Reddy＇s　higher　shear　deformation　theory,　von　Kármán　nonlinear　theory,　as　well　as　general　geometric　imperfection　function.　The　thermal　effect　on　the　material　properties　and　structural　rigidity　is　also　taken　into　account　in　this　model.　The　Newmark　method　and　Newton–Raphson　iterative　method　are　employed　to　solve　the　nonlinear　motion　equation　of　the　sandwich　beam.　In　numerical　examples,　the　dynamic　response　of　the　sandwich　beam　under　two　types　of　load,　i.e.　moving　load　and　impulse　load,　are　discussed　in　details.　The　influences　of　various　factors　(such　as　material　parameter,　geometric　imperfection,　and　thermal　condition)　on　the　nonlinear　dynamic　behaviors　of　the　sandwich　beam　are　elaborately　investigated.　The　numerical　results　show　those　factors　can　play　significant　roles　in　the　bearing　ability,　structural　stiffness,　or　nonlinear　dynamic　behaviors　of　the　sandwich　beam　in　certain　conditions.　Some　key　conclusions　on　the　influences　are　drawn　from　the　numerical　results,　which　can　be　a　useful　reference　for　future　investigations.　©　2023　Elsevier　Masson　SAS