Abstract: The microstructure and mechanical properties of TC17 titanium alloy with and without laser shock peening (LSP) were examined and compared. The titanium alloy samples were laser shock peened with different impacts at the same power density. Microstructure, microhardness and residual stress of TC17 titanium alloy introduced by LSP with different impacts were discussed by scanning electron microscopy(SEM), transmission electron microscope(TEM), X-ray diffraction(XRD), residual stress tester and sclerometer. The results indicate that a great deal of high-density dislocations and grain refinement are generated in the material surface layer. After 3 impacts LSP, there are nanocrystals in the LSP zone. The microhardness and residual stress value increase with greater impacts, and the variational trend with the depth is the same. Compared with the unsettled samples, the microhardness of TC17 titanium alloy treated by 5 impacts LSP has been increased by 20.7% at the surface, with a 300 m depth affected layer. A high compressive residual stress about 644.3 MPa is introduced with an increasing plastically affected layer by 5 impacts, and the affected depth increases to 1.9 mm.