Abstract: Based on the synchrotron radiation X-ray computed tomography technology and the in-situ mechanical loading test system, the macro-meso structures of Nitrate Ester Plasticized Polyether (NEPE) solid propellant at compression rates of 0.1 mm/s, 1 mm/s and 5 mm/s were in-situ observed. Meanwhile, typical damages and its evolutionary behaviors were analyzed. The macroscopic deformation of solid propellant as well as the distribution and propagation patterns of internal micro-cracks were explored. Results show that most of the micro-cracks nucleate and grow at the interface between filled particles and the matrix of solid propellant, and the evolution of meso-pores is rate-dependent. In contrast to the continuous growth of damage under tensile loading, the nucleation, growth and closure of pores occur simultaneously during compression. Under high-rate uniaxial compressive loading, solid propellant generates the characteristic trumpet-shaped deformation. The spatially distributed cracks mostly located around solid propellant. Macroscopic damage of sur-faces is caused by the propagation of micro-cracks between the near-surface particles and the matrix. The propagation of micro-cracks is related to the spatial location of filled particles in solid propellant. There are transversal and axial propagation modes of cracks under dynamic compressive loading. The transition from the vertically oriented crack to the horizontally oriented crack in matrix leads to closure of the crack.