Abstract: The laser shock peening (LSP) was applied on TC6 titanium alloy, the distribution of the residual stress in laser shock peened layer were tested, and the microstructure was observed by transmission electron microscopy. The results show that the optimal power density of laser shock peened layer of TC6 titanium alloy was 4 GW·cm-2, LSP could cause high residual stress field on material surface, and the residual stress was as high as 530.4 MPa. High density dislocation and nanocrystalline were found on titanium alloy surface after laser shock peening, and the nanocrystalline size was 10-100 nm.