The　piezoelectric　stack　energy　harvester　(PSEH)　is　often　used　to　transform　ambient　large　amplitude　vibrational　energy,　such　as　road　vibrations　and　pressure　fluctuations,　because　of　its　ability　to　withstand　large　external　excitation　force.　However,　due　to　the　high　natural　frequency　of　the　piezoelectric　stack,　it　is　difficult　to　generate　resonance　phenomenon,　which　leads　to　low　energy　efficiency　for　the　energy　harvester.　In　this　paper,　a　piezoelectric　stack　energy　harvester　with　force　magnification　frame　(FMF)　is　proposed　and　studied　for　energy　harvesting　from　low-frequency　pressure　ripples.　First,　a　force　magnification　frame　is　designed　to　enhance　the　pressure　transferring　ability.　The　FMF　is　able　to,　not　only　amplify　the　exciting　force　acting　on　the　piezoelectric　stack　but　also　decrease　the　natural　frequency　of　the　PSEH.　Based　on　finite　element　method　(FEM)　analysis,　the　natural　frequency　of　the　PSEH　with　FMF　is　obtained.　The　natural　frequency　of　the　PSEH　is　successfully　reduced,　and　the　open-circuit　voltage　output　of　the　PSEH　under　low-frequency　resonance　conditions　is　much　higher　than　for　off-resonance　conditions.　The　results　validate　that　the　PSEH　with　FMF　is　efficient　for　lower　frequency　vibration　environments.　©　Published　under　licence　by　IOP　Publishing　Ltd.