The study of damage mechanisms and its evolution of explosives is of great importance for the safety evaluation of explosive materials. A long-pulse low-velocity gas gun with a gas buffer was used to impact explosive samples. The explosives used include cast Comp. B and hot pressed PBXN-5. Different projectile velocities were used to achieve different damage degree in samples and the stress history of samples in the process of dynamic loading was recorded. The microstructure of samples before and after impact were studied by use of Scanning Microscopy (SEM) and Polarized Light Microscopy (PLM). In addition, the density and ultrasonic wave attenuation of samples before and after impact loading were examined. The results show that both Comp. B and PBXN-5 exhibit similar damage characteristics of brittle materials. However, due to the difference in compositions, Comp. B and PBXN-5 also exhibit different damage characteristics.