The molding granule is an intermediate for polymer-bonded explosive （PBX） components. Characterization of the physical parameters of granular system is of great significance to understanding the influence of different granule structure on the performance of PBX components. X-ray computed micro-tomography （XCT） and CT image processing were used to non-destructively characterize physical parameters （including granule diameter， volume fraction， porosity， sphericity and intrinsic density） of the granular random packing systems. The average granule diameter of granular systems is up to 1.04 mm， the volume fraction is up to 68.7%， the lowest porosity is 1.04%， the highest average sphericity is 0.93， and the highest density is 1.44 g·cm^-3. Results show that the type of binder， explosive crystal composition， explosive crystal ratio and granulation process in the formulation of molding granules have important influences on the physical parameters of the granular system. Moreover， there is a correlation between physical parameters of granular systems. The more dispersed diameter distribution of granular system leads to the larger the average surface area of granules. The larger average granule diameter and lower average sphericity of granular system result in the higher porosity of the granules. The volume fraction of granular systems with larger average granule diameter is higher， and the volume fraction of the granule accumulation is independent of the sphericity when the average sphericity is large. This work provides a basis for understanding the physical parameters of random packing system of modeling granules and the in-depth study of the relationship between granular structure and material properties.