The　superplastic　deformation　and　microstructure　evolution　of　a　new　near-　a　TNW700　titanium　alloy　with　shortterm　service　temperature　up　to　700　degrees　C　were　systematically　investigated　in　the　temperature　range　of　900-975　degrees　C　and　strain　rate　range　of　0.0005-0.01s(-1).　The　results　illustrate　that　TNW700　alloy　has　excellent　superplasticity　with　elongation　above　300%　and　m　value　above　0.41　at　900-950　degrees　C,　and　the　maximum　elongation　of　523%　is　obtained　at　950　degrees　C-0.001s(-1)　due　to　the　appropriate　grain　size　and　phase　ratio.　In　addition,　TNW700　alloy　exhibits　high　temperature　softening　and　strain　rate　hardening　behaviors.　The　increase　of　ss　phase　volume　fraction　induced　by　dynamic　phase　transformation　is　a　crucial　cause　for　flow　softening,　and　this　phenomenon　is　accelerated　with　increasing　temperature　and　decreasing　strain　rate.　The　refinement　of　primary　a　grains　and　the　inconspicuous　growth　of　ss　grains　at　lower　temperatures　are　favorable　for　grain　boundary　sliding　and　superplasticity　enhance,　whereas　the　overgrowth　of　ss　grains　at　975　degrees　C　results　in　superplasticity　absence.　The　decrease　of　dislocation　density　in　primary　a　grains　caused　by　strain　partitioning,　dynamic　recovery　(DRV)　or　dynamic　recrystallization　(DRX)　is　another　important　factor　for　high　temperature　softening;　the　increase　of　dislocation　density　and　velocity,　and　the　decrease　of　annihilation　time　contribute　to　strain　rate　hardening.　The　appearance　of　random　texture　indicates　the　activation　of　grain　boundary　sliding　(GBS)　and　grain　rotation.　GBS　is　the　overarching　mechanism　of　superplastic　deformation　of　TNW700　alloy,　accompanied　by　grain　rotation,　dislocation　movement,　dynamic　phase　transformation　and　grain　refinement　or　coarsening.