A　novel　energy-efficient　hybrid　multi-bit　Sigma-Delta　modulator　with　a　reusable　successive　approximation　register　(SAR)　quantizer　is　proposed.　By　reusing　the　SAR　quantizer,　sampling　capacitors　in　the　first　integrator　of　the　modulator　could　be　eliminated　and　almost　rail　to　rail　input　signal　range　could　be　achieved　by　the　modulator　without　the　requirement　of　a　high-swing　analog　adder　in　front　of　the　quantizer,　which　is　usually　power　hungry　in　multi-bit　modulators.　In　this　way,　small　capacitors　could　be　used　to　meet　the　thermal　noise　requirements,　thus　reducing　the　power　and　area　consumption.　With　an　improved　switching　procedure,　only　a　half　number　of　the　unit　capacitors　are　needed　in　the　SAR　quantizer,　which　further　reduce　the　area　consumption.