The aim of this study was to fabricate moisture-proof, phase-stabilized, ammonium nitrate/potassium nitrate (AN/PN) particles, with a polymer used as the moisture-proofing agent. The particles were prepared with a spray drying technique. Water solutions (or water dispersions) containing AN/PN and one of five different types of polymer were spray-dried, which produced white powders with particle diameters of approximately 20-40m. Scanning electron microscopy and energy-dispersive X-ray spectroscopy indicated that each component was homogeneously distributed throughout the particles. The particles exhibited little aggregation compared to the reagent AN, even when left for 7d or more. In addition, the moisture absorption of the particles at less than 40% relative humidity (RH) was lower than that of the polymer-free particles. Even under high-moisture conditions (83% RH), the particles did not deliquesce immediately, and they retained their original shape for 30-60min, whereas the polymer-free particles were transformed into droplets within 5min.