An efficient magnetic montmorillonite (Fe3O4/MMT) composite with the function of adsorption and degradation of organic pollutants was successfully prepared. The degradation effects and mechanisms of enrofloxacin (ENR) by Fe3O4/MMT were investigated. With the synergistic combination of the excellent adsorption and catalytic performance of the Fe3O4/MMT, ENR was adsorbed on the surface of Fe3O4/MMT, and then quickly degraded insitu by the active radicals produced on the material surfaces in the presence of persulfate (PS). At an initial ENR concentration of 30 mg/L, the ENR degradation efficiencies were maintained above 90% in 60 min by using 0.1 g/L Fe3O4/MMT to catalyze PS (5 mM). The effects of Fe3O4/MMT dosage, PS concentrations, pH, inorganic anions and natural organic matters on the ENR degradation kinetics and removal efficiency were studied. High catalytic activity of Fe3O4/MMT could be achieved for the degradation of ENR in water under acidic condition. The Fe3O4/MMT exhibited stable performance during three reuse cycles with minor Fe leaching. Overall, our study indicated that the Fe3O4/MMT composite had a promising application for the removal of pharmaceuticals from water.