The　crack　nucleation　mechanism　of　Ti60　titanium　alloy　under　ultrasonic　fatigue　loading　at　different　temperatures　was　investigated.　The　results　show　that　there　are　two　different　crack　nucleation　mechanisms　at　RT,　300　°C,　and　400　°C,　i.e.,　the　oversized　facet　and　oxide　shedding　crack　nucleation　mechanisms.　Almost　all　fatigue　cracks　initiate　in　the　form　of　oversized　facets　at　RT.　At　300　°C,　the　crack　initiates　at　the　oversized　facet　under　the　low　load　test,　while　the　crack　initiates　at　the　oxide　shedding　site　under　the　high　load　test.　At　400　°C,　all　the　fatigue　cracks　initiate　at　the　place　where　the　oxide　shedding.　Higher　temperature　and　applied　stress　will　help　the　oxide　shedding　crack　nucleation　mechanism　to　become　dominant.　©　Published　under　licence　by　IOP　Publishing　Ltd.