Poly(phthalazine　ether　sulfone　ketone)　(PPESK)　is　a　new　type　of　thermoplastic　resin　materials　with　high　temperature　resistance　and　corrosion　resistance.　However,　the　failure　evolution　regularities　of　PPESK　at　different　temperatures　still　remain　poorly　understood,　which　greatly　limits　the　application　of　this　composite.　Therefore,　quasi-static　tensile/bending　tests　and　microscanning　microscopic　characterization　were　used　to　study　the　multi-scale　failure　constitutive　equation　of　PPESK.　Based　on　cross-scale　experimental　observation　methods,　the　spatial　damage　morphology　of　materials　at　different　temperatures　is　explored,　and　the　temperature　boundary　effect　of　PPESK　is　proposed　to　reveal　the　failure　and　failure　mechanisms　of　materials　in　a　wide　temperature　range.　The　initiation　and　evolution　of　pores　at　the　micro　scale　of　PPESK　and　the　cumulative　damage　caused　by　craze　propagation　and　cracking　are　essential　factors　of　material　failure,　which　also　exhibit　strong　temperature　sensitivity.　The　specific　manifestation　is　the　high-temperature　viscous　flow　effect　of　the　resin　at　the　micro　scale,　as　well　as　the　gradual　evolution　trend　of　quasi-brittleness　and　viscoelastic-plasticity　between　the　295　K–472　K　temperature　range　in　the　macro　performance,　which　increases　its　plastic　deformation　ability　by　1–5　times.　Specifically,　the　mechanism　of　cross-scale　micro-pore　initiation　and　crack　propagation　was　introduced,　and　a　cross-scale,　fully　three-dimensional　failure　damage　evolution　constitutive　model　of　PPESK　was　constructed　for　the　first　time　in　a　wide　temperature　range.　The　secondary　development　of　the　material　constitutive　model　in　the　finite　element　software　was　carried　out,　and　the　construction　of　the　constitutive　equation　of　the　PPESK　cross-scale　failure　was　completed.　Finally,　the　mapping　relationship　between　the　material＇s　crack　failure　form,　mechanical　behavior,　and　the　constitutive　model　was　further　verified　by　experiments.　It　is　established　that　the　proposed　PPESK　multi-scale　failure　constitutive　model　enables　one　to　effectively　describe　the　complex　mechanical　response　and　failure　law　of　thermoplastic　resin　materials　under　temperature　gradients.　Moreover,　this　theoretical　tool　is　promising　for　the　design　of　independently　controllable　high-temperature　resistant　thermoplastic　resin　materials,　thereby　providing　important　guidance　means　for　engineering　applications.　©　2023