In current study, the laser shock processing (LSP) technique of high energy and short pulse duration is adopted. The substructural transformation characteristics and mechanisms of 2Cr17Mn15Ni2N austenitic stainless steel, subjected to ultra-high strain-rate and impact stress in excess of dynamic yield strength of the target, are investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM) technology. It is found that the crystallinity in the treated zone is declined, and the size of subgrains ranging from 0.1 to 0.5 μm and the regular arrangement of chapped substructures are formed in the treated region. The hardness in the impacted zone increases apparently and the deformation depth reaches 0.25 mm. Meanwhile, the deformation-lagged annealing twins, microbands, dislocation blocks, streak-like subgrains, slip-type stacking faults, and so on, have been observed in the subsurface of the treated regions. No deformation twin and ε(α) martensite phase are identified. It shows that the ultra-high strain rate induced by LSP plays the crucial role accounting for the unique substructures of the impacted austenitic stainless steel.