TC11 titanium alloy was treated by laser shock peening(LSP) and microstructure, residual stress and microhardness with and without LSP were examined and compared via transmission electron microscope(TEM), X-ray diffractometer and microhardness tester. The TEM results indicate that a great high density of dislocations are generated and evolve into the dislocation wall, sub-boundary and grain boundary. The nanocrystallines are formed and become smaller and more uniform with greater impacts. A high compressive residual stress above -540MPa is introduced with an increasing plastically affected layer with different impacts. The microhardness test result shows that LSP can obviously increase the hardness by 20 percent or so, and the affected depth increases with the impact from 600μm to 1200 μm.