To recover Au(III) from an acidic chloride-containing solution efficiently, an ionic liquid absorbent (CMPS-IL) was synthesized by grafting N-methyl imidazole onto chloromethylated polystyrene beads (CMPS). The adsorption capacity, selectivity, and reusability were systematically evaluated by a series of adsorption experiments. The maximum adsorption capacity reached up to 516.5 mg g⁻¹ at 318 K. The adsorbent can selectively recover Au(III) from binary system solutions with a higher separation factor β_Au/M (10⁴–10⁶). Moreover, the adsorption–desorption cycles (7 cycles) showed that the CMPS-IL maintained a stable adsorption performance and high adsorption efficiency. Finally, the adsorption mechanism of CMPS-IL for Au(III) was investigated by SEM, TEM, XPS, and FT-IR, then proposed with a combination of electrostatic interactions and d–π interaction between imidazolium and AuCl₄⁻. This study provides an easily-prepared and economical adsorbent for Au(III) with high selectivity and large adsorption capacity to boost its practical applications.