Abstract: In order to study effect of laser shock peening(LSP) on residual stress, micro-hardness and metallographic structure evolution of Ti-6Al-4V titanium alloy at different temperatures, Ti-6Al-4V alloy samples were treated by LSP using high power and short pulse Nd:YAG laser and then were annealed at the temperatures of 400℃, 500℃, 550℃ and 600℃ for 1h respectively. Residual stress was measured by X-ray diffraction (XRD) method and metallographic structures were characterized by scanning electron microscopy (SEM) and transmission electron microscope (TEM). The correlations between strengthening effect and grain size, dislocation were studied based on microstructure observations. The results indicate that high amplitude of residual compressive stress is induced on the surface via laser shock peening and micro-hardness is increased significantly. After the 1h preheating of 550℃, the effect depth of residual stress is about 100μm. After the 1h preheating of 400℃ and 600℃, micro-hardness on the specimen surface declines 8.3HV and 20.1HV respectively. After heat processing, grain size has an increasing trend in general. LSP can effectively improve mechanical property of Ti-6Al-4V titanium alloy at different temperatures.