We describe for the first time a spray‐recrystallization method to prepare sub‐micrometer N‐amino‐2,4‐dinitroimidazole (ADNI) and test its critical diameters below 3 mm. The uniform sub‐micrometer ADNI has better sensitivity to short impulse shock waves with the 50% and 99.9% initiation currents at 2.45 kA and 2.67 kA, respectively, which is much better than sub‐micrometer LLM‐105 (3.11 kA and 3.46 kA, respectively) and DAAF (3.7 kA and 4.75 kA, respectively). The detonation velocity for ADNI (7.8 km⋅s−1 at a density of 1.67 g⋅cm−3) is greater than that of LLM‐105 (7.54 km⋅s−1 at the density of 1.63 g⋅cm−3) and haxanitrostilbene (HNS) (6.8 km⋅s−1). ADNI also has a higher decomposition temperature (Td =265.8 °C) and a better thermal stability (5S shotpoint of 312 °C) with low impact, friction, and electric spark sensitivities (>40 N, >360 N, and 2.20 J). These metrics are comparable to LLM‐105 (0–30 N, >360 N, and 1.02 J) and HNS (26 N, 240 N, and 1.77 J). The high stability and good detonation properties of sub‐micrometer ADNI clearly shows that it is insensitive to impact stimulus and long pulse stimulation, while also being sensitive to short impulse shock waves. This suggests that it is a promising initiating explosive for slapper detonators.