The effects of high cycle fatigue-low fatigue life(HCF-LCF) on titanium alloy (TC4 and TC11) were researched experimentally with foreign object damage (FOD) simulation through pendulum method and air-gas gun method and the features of these two different damage notches were analyzed and compared. Fatigue tests on nondestructive and destructive specimens were further conducted to analyze and compare the effects of FOD on the titanium alloy fatigue life.The conclusions show that:pendulum impact test method simulation lacks of representativeness

while air-gas gun projectile method simulation is much closer to the truth; FOD leads to severe decline of HCF-LCF life of titanium alloy

and air-gas gun projectile method simulation decreases the titanium alloy fatigue life from 105 to 104 order of magnitude.