Abstract: Stainless-steel Ultra-thin strips, with their ultra-thin profile, high specific strength, excellent formability, and inherent corrosion resistance of the stainless-steel matrix, have emerged as an ideal core material for honeycomb sandwich structures. To investigate the dynamic response characteristics, failure modes, and impact energy dissipation mechanisms of stainless steel ultra-thin strip honeycomb sandwich structures under impact, this study proposes the fabrication of honeycomb cores using 50 μm-thick SUS304 ultra-thin stainless-steel strips as the substrate material, manufactured through roll forming and laser spot welding processes. Carbon fiber reinforced polymer (CFRP) face sheets/stainless steel ultra-thin strip honeycomb sandwich beams were prepared through hot-pressing composite process. Drop-weight impact tests were conducted within 100 J-400 J energy range for three-point bending impact experiments. A finite element model of the sandwich beam was established using ABAQUS/Explicit to comprehensively analyze its response under impact loading. Results indicate that the load-deflection curves of the sandwich beams under various impact energies exhibit three characteristic stages: initial loading, stable progression and unloading recession. When impact energy increased from 100 J to 400 J, the peak load rose by 22.7%, while rebound displacement decreased from 0.94 mm to 0.63 mm, accompanied by a 15.1% reduction in energy absorption efficiency. The primary failure modes include CFRP face sheet delamination, fiber/matrix damage and fracture, along with plastic crushing of the honeycomb core. Plastic deformation of the honeycomb core (57%-69%) and delamination damage in CFRP face sheets (11%-23%) constitute the main energy dissipation mechanisms across 100 J-400 J impact energies. The bending damage failure of stainless steel ultra-thin strip honeycomb sandwich beams can be divided into three stages: elastic deformation, face sheet fracture, and core crushing accompanied by structural collapse. As the impact energy increases, their bending resistance significantly improves, while resilience diminishes and energy absorption efficiency decreases. The primary mechanisms for energy dissipation arise from the synergistic effect between the plastic crushing of the honeycomb core and the interlaminar damage in the CFRP face sheets.