The　buckling-restrained　brace　(BRB)　serves　as　an　effective　energy　dissipation　component,　commonly　integrated　into　structural　designs　to　enhance　earthquake　resilience.　However,　excessive　strength　of　the　BRB　may　elevate　the　internal　forces　within　its　adjacent　structural　elements　and　in　return　compromise　its　energy　dissipation　efficiency　during　severe　seismic　events.　This　study　aims　to　propose　a　double-stage　capacity-adjustable　buckling-restrained　brace　(i.e.,　CABRB),　which　incorporates　a　sacrificial　component　and　an　energy　dissipation　BRB　that　collaborate　in　parallel.　In　contrast　to　conventional　BRBs,　the　strength　and　stiffness　of　the　CABRB　can　be　independently　tailored　by　separately　designing　its　sacrificial　component　and　BRB,　allowing　the　CABRB　to　exhibit　double-stage　mechanical　properties　under　various　intensities　of　earthquakes.　Specifically,　under　design　basis　earthquakes　(DBEs),　the　brace　maintains　sufficient　stiffness　to　control　the　structural　deformation,　while　under　maximum　considered　earthquakes　(MCEs),　it　reduces　the　yield　strength　to　enhance　the　energy　dissipation　efficiency.　First,　the　detailed　configurations　and　working　mechanism　of　the　CABRB　are　presented.　Two　CABRBs　with　different　types　of　sacrificial　plates　are　developed.　Quasi-static　tests　are　conducted　on　the　sacrificial　plates,　the　BRB,　and　the　CABRBs　to　validate　the　double-stage　mechanical　behavior　of　the　CABRB.　Subsequently,　analytical　equations　for　quantifying　the　mechanical　behavior　of　the　CABRB　are　derived　using　the　principle　of　virtual　work　and　incremental　analysis.　The　accuracy　of　these　equations　is　validated　through　comparison　with　experimental　data.　The　results　indicate　that　the　sacrificial　plate　with　obround　openings　surpasses　those　with　long　rectangular　openings.　Furthermore,　the　CABRB　exhibits　stable　seismic　mechanical　behavior,　positive　design　adaptability,　and　distinctive　adjustable　mechanical　characteristics,　promising　to　meet　the　multi-level　seismic　performance　requirements.