The Laser Shock Peening (LSP) is commonly used to strengthen the surface of materials. However, the microstructures after LSP impact are complex due to the intense forces involved. In this study, we explore how martensitic microstructures evolve in a half cylinder of NiTi under LSP impact using the Electron Backscattered Diffraction (EBSD) technique. A gradient of orientation of martensite is observed after LSP impact: the upper layers show highly oriented martensite, characterized by blocky shapes; while the lower layers display more uniform and needle-like martensitic structures. To better understand these microstructural changes, we used Finite Element (FE) simulations to analyze the stress distribution caused by the LSP. From the simulated stress conditions, the reorientation and changes of microstructures of the martensite was satisfactorily predicted by using the Interaction Work (IW) model. Overall, this comprehensive analysis provides valuable insights into the understanding of microstructural changes induced by LSP impact in martensitic NiTi alloys.