Magnesium　(Mg)　alloys　are　becoming　popular　in　lightweight　manufacturing　due　to　their　low　density　and　high　specific　strength.　However,　insufficient　slip　systems　result　in　poor　plasticity　of　Mg　alloys　at　room　temperature.　Therefore,　an　ultrasonic　energy　field　combined　with　thermal　field　is　introduced　to　assist　the　deformation　of　AZ31　Mg　alloy　to　improve　its　plasticity.　Firstly,　ultrasonic　vibration　(UV)-assisted　tensile　tests　at　different　temperatures　(130–150　°C)　are　conducted　to　investigate　the　effect　of　UV　on　material　behaviour　and　the　activation　of　dynamic　recrystallization　(DRX).　Then,　the　influences　of　UV　on　the　mechanical　properties　and　microstructure　of　the　material　at　150　°C　are　investigated　by　varying　the　parameters　of　ultrasound　amplitude,　strain　rate,　and　vibration　interval.　The　results　reveal　that　applying　UV　can　activate　DRX　at　a　relatively　lower　temperature　compared　with　that　without　UV.　Superimposing　a　certain　amount　of　ultrasonic　energy　on　this　material　at　warm　conditions　reduces　flow　stress　and　increases　elongation.　In　the　intermittent　ultrasonic　vibration　(IUV)　tests,　the　DRX　percentage　and　elongation　first　increase　and　then　decrease　as　the　vibration　interval　increases.　The　elongation　of　specimens　with　appropriate　vibration　intervals　even　exceeds　that　of　specimens　with　continuous　ultrasonic　vibration　(CUV).　However,　CUV　is　more　effective　than　IUV　in　reducing　ultimate　tensile　strength　at　different　amplitudes　or　strain　rates.　©　2024