Abstract: Porous ammonium nitrate offers specific operational advantages over conventional ammonium nitrate due to its porous structure, but its higher transportation costs increase overall operational expenses. This paper proposes a method to transform conventional ammonium nitrate or its solution into porous ammonium nitrate through modification, providing new theoretical support for optimizing ammonium nitrate performance and controlling costs. This study utilized ion-exchange surfactant (PST) as an additive to prepare porous granule-modified ammonium nitrate via spray granulation. The effects of varying PST concentrations (0%-0.4%) on ammonium nitrate's pore structure, oil absorption rate, thermal stability, and explosive properties were systematically investigated. Results indicate that increasing PST content gradually transforms dense ammonium nitrate particles into a porous structure with distinct interconnected pores. Thermal stability remains essentially unchanged, and the matrix chemical composition undergoes no fundamental alteration, though water adsorption decreases. The modified samples exhibited enhanced binding capacity with the oil phase. The detonation velocity of the assembled charge increased from “failed to detonate normally” in the unmodified state to 2831.85 m·s⁻¹. Trace amounts of PST can induce the formation of a porous structure in ammonium nitrate without significantly compromising thermal safety, while markedly improving detonation velocity performance, demonstrating potential for engineering applications.