The explosive HNS-IV has been proven to be insensitive to shock, percussion, heat, and friction among polymorphs of HNS. According to the US military standard MIL-E-82903, the surface area of HNS-IV must be 5.0 to 25.0 m(2)/g. Thus, the micronization of its particles in re-crystallization process is a key step. The solvent/anti-solvent method is used for re-crystallization of HNS-IV particles because user-friendly, inexpensive and efficient. A successful re-crystallization depends on the proper choice of solvent. Among studied solvents, N,N-dimethylformamide (DMF) is selected based on its solubility for HNS that is obtained 7.23 g per 100 mL at 100 degrees C. Taguchi experiment design method is used to optimize the solvent/anti-solvent re-crystallization process. The three parameters of volume ratio of anti-solvent to solvent, temperature of solvent and temperature of anti-solvent are optimized. The bulk density (B.D) of re-crystallized of HNS-IV particles is used as a signal for optimization with the concept of "the larger-the-better". The optimized parameters are volume ratio 20 to 1 for anti-solvent to solvent and temperatures of 100 and 5 degrees C, respectively, for solvent and anti-solvent. BET (Brunauer-Emmett-Teller) method shows the specific surface area 12.7 m(2)/g for re-crystallized particles. Also, SEM images indicate a thin platelet with size 5-10 mu m for micronized HNS-IV product.