Different　from　strengthening　key　structural　members　against　potential　blast　load　to　make　it　thicker　and　stronger,　an　alternative　approach　of　blast　mitigation　is　to　apply　sacrificial　claddings　with　lightweight　core　to　the　exterior　of　existing　buildings　and　structures.　Selected　materials　and　structures　of　soft　resistance　and　low　density　undergo　large　deformation　with　almost　constant　stress　and　absorb　large　amounts　of　energy,　making　them　promising　for　structure　protection.　After　a　blast　attack,　replacing　the　sacrificed　and　damaged　core　with　a　new　one　immediately　resumes　the　blast　mitigation　capacity,　making　the　protection　resilient.　Applying　such　sacrificial　claddings　has　multiple　merits,　including　efficiency　in　protection,　sustainability,　and　flexibility.　However,　there　are　still　some　problems　to　be　addressed　before　such　claddings　can　be　successfully　applied　in　engineering　practice.　In　this　study,　a　criterion　based　on　energy　approach　is　established,　to　determine　the　effectiveness　of　blast　mitigation　with　lightweight　claddings.　The　analytical　model　incorporates　interaction　among　the　blast　load,　the　cladding　system,　and　the　protected　structure　member　which　is　simplified　as　an　SDOF　system.　The　underlying　mechanism　of　blast　mitigation　with　lightweight　claddings　is　analyzed　in　terms　of　energy.　Key　governing　factors　that　determine　the　protection　effectiveness　are　identified　and　their　influence　is　discussed.　(C)　2017　The　Authors.　Published　by　Elsevier　Ltd.　Peer-review　under　responsibility　of　the　scientific　committee　of　the　6th　International　Workshop　on　Performance,　Protection　&　Strengthening　of　Structures　under　Extreme　Loading