The fatigue crack growth rate of inertia friction welded joints of TC17 titanium alloy was studied. The microstructure and the fracture surface were analyzed by means of optical microscopy and scanning electron microscopy. The results show that the microstructure of TC17 titanium alloy is +phase with bigger grain. The microstructure of weld zone and heat affected zone is tiny phase and clear phase grain boundary,the original grain of weld zone is smaller, the original grain of heat affected zone is bigger. At room temperature;when K15 MPa·m1/2,the fatigue crack growth rate of weld zone is smaller;when K15 MPa·m1/2,the fatigue crack growth rate of weld zone is the largest. The next is heat af fected zone, the growth rate of parent metal is the smallest. At high temperature,the fatigue crack growth rate of different parts of welded joints shows little difference,but all lower than those tested at room temperature.