Multiphase　motor　drives　have　many　advantages　over　the　traditional　three-phase　motor　drives.　In　this　paper　we　firstly　deduce　the　mathematic　modeling　for　a　dual-three-phase　permanent　magnet　synchronous　motor　(PMSM)　according　to　vector　space　decomposition　theory.　Then,　a　sensorless　vector　control　based　on　the　Model　Reference　Adaptive　System　(MRAS)　is　developed　for　a　dual-three-phase　PMSM　and　the　system　stability　is　verified　by　Popov　super　stability　theory.　Furthermore,　a　new　and　very　simple　initial　rotor　position　estimation　method　is　proposed　by　means　of　DC　excitation　without　any　sensors.　Finally,　a　dual-three-phase　PMSM　experimental　prototype　is　designed　and　fabricated　in　the　laboratory.　The　simulation　and　experimental　results　are　presented　to　demonstrate　the　effectiveness　of　the　proposed　scheme.