The evolution of dislocation patterns and the properties of hexagonal close-packed (HCP) structure in TC4 dual-phase titanium alloy under ultra-high strain rate plastic deformation were studied via laser shot peening (LSP) treatment. The results show that, the compressive residual stress can be generated and the grains can be refined by the LSP treatment. Moreover, with the LSP times increasing, more finer grains, larger compressive residual stress, and the depth of LSP-induced compressive residual stress are generated. The evolution of dislocation patterns in the HCP structure subjected to LSP treatments can be described as follows. For the as-machined specimen (with an average grain size d=21.33 μm), dislocations and dislocations are dominant. While for the LSP-1 specimen (with an average grain size d=9.65 μm), parts of unstable dislocations are decomposed into dislocations and dislocations. After massive LSP treatments (with an average grain size d=4.55 μm), more slip systems are activated, and dislocations and dislocations are dominant eventually. In addition, Values of hardness and elastic modulus of HCP structure increase with the increase of strengthening times, but the increment decreases simultaneously.