Organic micropollutant is an emerging problem in drinking water treatment. Oxidation by peroxymonosulfate activation is an efficient measurement for the degradation of organic micropollutants. However, the cost of current catalysts is high, and their preparation and regeneration processes are complicated. This work attempts to modify the natural montmorillonite with Fe(III) salt, which is used as the peroxymonosulfate activator for the degradation of bisphenol A (BPA) in drinking water. Results show that BPA was quickly adsorbed onto the surface of montmorillonite, and the removal rate was up to 96.4% in 1 h. The nanoscale interlayer of Fe(III)-modified montmorillonite (Fe-MMT) accelerated the transformation of electrons between Fe(III) and PMS, which was beneficial to the decomposition of PMS to generate HO· and SO₄·^- radicals, accelerating the degradation of BPA in water. In addition, the mesoporous layer structure of Fe-MMT could effectively inhibit the effects of humic acids on the PMS activation. Fe-MMT with easy preparation and regeneration processes can be used as the PMS activator in drinking water treatment.