Based　on　the　topology　of　back-to-back　convertor,　a　regenerative　braking　strategy　used　for　Permanent　Magnet　Synchronous　Motor　(PMSM)　is　presented　in　this　paper.　According　to　this　strategy,　without　dc　link　braking　resistor,　PMSM　can　operate　in　four-quadrants　stably,　and　switch　in　different　quadrants　continuously.　Based　on　Model　Reference　Adaptive　System　(MRAS)　theory,　a　rotational　inertia　onlineobserver　is　designed,　and　an　energy　manager　strategy　is　obtained　using　the　observed　inertia　value.　The　strategy　is　verified　in　Matlab/　Simulink.　Then　in　a　4kW　PMSM　experiment　platform,　the　regenerative　braking　strategy　is　implemented.　The　results　of　experiment　show　that　the　regenerative　braking　strategy　can　be　used　in　PMSM　forward　and　reverse　operation　effectively,　which　is　the　foundation　of　the　further　industrial　application.