A　novel　oscillator　structure　consisting　of　a　bimorph　piezoelectric　cantilever　beam　with　two　steps　of　different　thicknesses　is　proposed　to　improve　the　energy　harvesting　performance　of　a　vibration　energy　harvester　(VEH)　for　use　in　low-frequency　vibration　environments.　Firstly,　the　piezoelectric　cantilever　is　segmented　to　obtain　the　energy　functions　based　on　the　Euler-Bernoulli　beam　assumptions,　then　the　Galerkin　approach　is　utilized　to　discretize　the　energy　functions.　Applying　boundary　conditions　and　continuity　conditions　enforced　at　separation　locations,　the　coupled　electromechanical　equations　governing　the　piezoelectric　energy　harvester　are　introduced　by　means　of　the　Lagrange　equations.　Furthermore,　expressions　for　the　steady-state　response　are　obtained　for　harmonic　base　excitations　at　arbitrary　frequencies.　Numerical　results　are　computed,　and　the　effects　of　the　ratio　of　lengths,　ratio　of　thicknesses,　end　thickness,　and　load　resistance　on　the　output　voltage,　harvested　power,　and　power　density　are　discussed.　Moreover,　to　verify　the　analytical　results,　finite　element　method　simulations　are　also　conducted　to　analyze　the　performance　of　the　proposed　VEH,　showing　good　agreement.　All　the　results　show　that　the　present　oscillator　structure　is　more　efficient　than　the　conventional,　uniform　beam　structure,　specifically　for　vibration　energy　harvesting　in　low-frequency　environments.