Abstract: The TC4 Welded Joints were subjected to surface nano-crystallization by using High Energy Shot Peening(HESP) technology, and the changes of the microstructure, grain size, the hardness and residual stress were examined by using OM, XRD and hardness tester. The results show that the plastic deformation layer with a certain thickness could be achieved at the surface of TC4 welded joints after HESP. The coarse-grained microstructure of top-surface layer of welded joint can be refined into nano-scale after the HESP treatment, The same hardness can be found for the nanostructured surface layers of the base metal, HAZ and weld of TC4 respectively, which is much higher than that of the sample before the HESP treatment. The tensile residual stress turned into compressive residual stress after the HESP treatment. Homogenization of microstructure and properties of the surface layers of TC4 welded joint are achieved.