In　this　paper,　a　highly　efficient　differential　rectifier　for　passive　radio　frequency　(RF)　energy　harvesting　device　is　designed.　The　circuit　uses　the　differential-drive　CMOS　to　reduce　the　RF　energy　loss　caused　by　the　MOS　threshold　voltage　during　rectification　and　improve　the　rectification　efficiency　of　the　circuit.　The　circuit　was　fabricated　with　a　0.35　mu　m　CMOS　process　and　the　overall　RF-DC　power　conversion　efficiency　for　a　DC　output　power　of　160　mu　W　(2.5V　and　64　mu　A)　is　about　50%.　When　high　voltage　is　needed　for　stimulator　output,　the　maximum　efficiency　for　a　4V　DC　voltage　reaches　66.5%　at　-　3dBm.　The　proposed　rectifier　allows　the　output　voltage　higher　than　6V.　It　is　suitable　for　such　applications　that　require　high　RF　input　power　such　as　implantable　medical　devices　(IMDs)　and　passive　industrial　sensor.