Abstract: Two types of hollow glass microspheres (HGMs) with different mechanical properties were selected as fillers to fabricate a series of HGMs/polyurethane (PU) composites with varying mass fractions. The uniaxial compressive mechanical properties of HGMs/ PU composites were investigated within the strain rate range of 10⁻³ to 1200 s⁻¹ using a universal testing machine and a split Hopkinson pressure bar (SHPB) apparatus. Stress-strain curves of HGMs/ PU composites at various strain rates were obtained, revealing the influence of strain rate, compressive strength, and mass fraction of HGMs on the yield strength of the composites. The microstructure and fracture morphology of the specimens were analyzed using SEM and CT , elucidating the deformation and failure mechanisms of HGMs/PU composites under different strain rates. The results show that: (1) The axial compressive mechanical properties of HGMs/PU composites exhibit a significant strain rate dependence. At low strain rates, the HGMs/PU composites demonstrate nonlinear viscoelastic mechanical behavior, while at high strain rates, it displays impact strengthening and stress relaxation features due to shock damage. A negative strain rate effect is observed at 1200 s⁻¹, and the strain rate sensitivity coefficient is independent of the HGM mass fraction. (2) The yield strength of HGMs/PU composites decreases with increasing HGM mass fraction, and this trend is closely related to the strain rate and the compatibility between HGMs compressive strength and matrix strength. (3) Analysis of the cross-sectional microstructure and fracture morphology of the specimen reveals that under quasi-static compression, the S15 HGMs undergo localized fragmentation within the composite, whereas the HGS5000 HGMs remain intact. Under impact compression, S15 HGMs experience severe fragmentation, and HGS5000 HGMs are penetrated by cracks, exhibiting a typical brittle vertical splitting failure mechanism.