The microstructure of TC18 titanium alloy was investigated by XRD，SEM and TEM. The impact toughness of the TC18 titanium with different notch depths was tested by instrumented pendulum impact tester, and the curve showing the impact process was gained. The fracture was analyzed by SEM. The results show that the impact toughness decreases as the notch depth increases, and the toughness of the specimen with 0.02 cm notch was much smaller than that with no notch. The specimen with no notch just curves without breaking.