A confined, quasi-static uniaxial compression method, named as the compressive stiffness test (CST), is promoted to evaluate the quality of different RDX crystalline particles which are obtained from commercial and reprocessed lots. This method is based on the fact that the fragmentation or fracture behavior in the compression process could be correlated to the external/internal defects of targeted crystalline particles. The quality difference between the commonly used RDX and reprocessed RDX can be easily discriminated by compaction curves and the defined initial secant modulus can be used as a quantitative parameter to grade RDX particles. ne results show that the RDX recrystallized from mixed solvents and spheroidized by treatment with solvent is of much higher quality than the commonly used RDX, and the particle size as well as external characteristics exert limited effects on the compaction curves, but the key factor is internal defects, which affect the coherence strength of RDX crystalline particles. Qualitative optical image analysis and quantitative particle apparent density measurements by liquid density gradient tubes also give consistent results with those from the CST.