This　paper　proposes　a　novel　tapped-inductor　bi-directional　BUCK/BOOST　(TI-B-BUCK/BOOST)　topology,　which　can　overcome　the　drawback　of　non-isolated　bi-directional　DC-DC　(BDC)　that　its　transfer　ratio　is　restricted　in　a　small　range.　This　paper　analyzes　the　principle　and　characteristics　of　TI-B-BUCK/BOOST　in　detail.　Then,　the　optimization　of　the　turn　ratio　of　tapped-inductor　based　on　power　loss　model　of　the　new　topology　has　been　done.　Computer　simulation　based　on　MATHCAD　and　experimental　result　on　a　prototype　built　in　lab　verify　that　TI-B-BUCK/BOOST　widely　extends　the　transfer　ratio　of　non-isolated　BDC　and　its　efficiency　is　much　higher　than　conventional　bi-directional　BUCK/BOOST.　©2008　IEEE.