maraging steel has ultra-high strength, hardness and excellent weldability, making it widely used in industrial and military fields such as vehicles, aerospace, protective armor and weapon systems, often facing dynamic service scenarios with high pressure and high strain rate. Therefore, investigating the damage behavior and structure evolution of maraging steel at high strain rates is crucial for evaluating its mechanical properties and service life under extreme conditions. In this study, spallation experiments have been performed on the heat-treated 18 wt% Ni-350 maraging steels (M350) fabricated by laser powder bed fusion (LPBF). Two different impact directions of the LPBF M350 were respectively subjected to impact loading with a peak stress of about 7.0 GPa - 10.5 GPa to assess the dynamic mechanical behavior under different impact pressures. The results showed that the samples with impact direction vertical build direction (5.01 GPa - 5.89 GPa) had higher spall strength than those with impact direction parallel build direction (4.53 GPa - 4.99 GPa), and the elastic limit and spall strength were better than most other metals, showing excellent impact resistance. The damage behavior of the heat-treated LPBF M350 was mainly crack propagation, propagation direction was along the {100} cleavage plane of the blocks, and some cracks turned at right angles, which appeared as transcrystalline brittle fracture. In the primary laths which contained high-density precipitates, dislocation slip cut the precipitates and eventually caused them to fracture in the process of impact deformation. Moreover, the original packet-block-lath hierarchical structure became more abundant after the impact loading, the existence of new laths at smaller scales were observed for the first time in maraging steels, and the secondary laths and tertiary laths were formed in the primary laths with almost no precipitates, the width of the laths was extended from hundreds to several nanometers, thus adding lots of LAGBs and strengthening the material through Hell-Petch effect.