A　lever-enhanced　negative　stiffness　isolator　(LENSI)　is　proposed　to　attenuate　the　longitudinal　vibration　of　a　shaft-plate　coupled　system　in　the　low-frequency　range.　The　isolator　comprises　a　rigid　lever,　an　isolator　mass　and　a　negative　stiffness　element,　installed　in　parallel　with　the　thrust　bearing.　The　dynamic　model　of　the　shaft-plate　coupled　system　is　formulated　using　the　Rayleigh-Ritz　method.　Longitudinal　acceleration　frequency　response　of　the　bearing　pedestal　and　mean　square　velocity　of　the　plate　are　used　to　evaluate　the　isolation　performance　of　the　proposed　isolator.　By　comparing　the　isolation　performance　of　LENSI　with　traditional　isolator　such　as　dynamic　anti-resonance　isolator　(DAVI)　or　absorber　such　as　dynamic　vibration　absorber　with　negative　stiffness　(DVANS),　the　superiority　of　the　LENSI　is　demonstrated.　A　parametric　study　is　presented　to　clarify　the　influence　of　the　isolator　parameters　on　its　isolation　performance.　It　is　shown　that　the　LENSI　is　capable　of　isolate　the　longitudinal　vibration　of　the　shaft-plate　coupled　system　with　a　much　lower　mass　ratio　in　the　low-frequency　range.