The study of the dynamic behavior of materials under impact conditions is crucial in aerospace and defense industries. These materials are subjected to high speed and hyper-velocity impacts, high temperature, high pressure, and considerable deformation. Notably, many crystal-structured steel plates exhibit similar variability when subjected to impact conditions. A current and cutting-edge topic in contemporary research is the exploration of the microstructure properties of steel plates with various crystal structures under impact. This study aims to investigate the microstructural change of various crystalline structural steel materials under impact loads with high velocities. Two typical crystalline structural steels, 304 and Q345 stainless steels, were tested in impact tests using a two-stage light-gas pistol. The microstructure features of the steel plates under impact were characterized and examined using characterization techniques like XRD, EBSD, and TEM. Under impact conditions, the 304 stainless steel plate did not show any significant flanging phenomena at the macro level. However, there is a minor degree of ε-martensite transition and micro α'-martensite transformation that occurs on 304 stainless steel plates. Austenite and martensite have a similar K-S orientation relationship. Under the impact condition, the Q345 steel plate displays macro-level flipping properties but no overt micro-level phase transition. However, the diffraction peak on the {110} crystal plane substantially increases, the space between crystal planes narrows, and the {200} crystal plane shows a considerable diffraction peak shift to the right, creating the grains' preferred orientation. The Q345 steel plate exhibits considerable crystal structure delamination under impact, whereas 304 stainless steel did not display significant crystal structure elongation. The two types of steel plates have various macroscopic fracture modes owing to their differing crystal structures. Specifically, the Q345 steel demonstrates plastic fracture properties, whereas 304 stainless steel displays almost brittle fracture characteristics. The twin grain boundary of austenite is where martensite forms based on the calibration of electron diffraction spots.