Abstract: Bimetallic Fe-Mn oxide (Fe-MnO_x) was prepared using the sol-gel method to take advantage of the ability of Fe and Mn ions to activate peroxymonosulfate (PMS) in a homogeneous system and avoid pollution caused by metal ions. The degradation process and mechanism were investigated for the removal of Acid Orange 7 (AO7) by using Fe-MnO_x as a catalyst to generate powerful radicals from PMS. The effects of ρ(Fe-MnO_x), ρ(PMS)₀ and ρ(AO7)₀ on the degradation of AO7 were tested. The results showed that with the ρ(Fe-MnO_x) from 50 mg/L to 200 mg/L, the degradation rate of AO7 increased from 53.74% to 96.65% at 35 min. However, no significant change in the degradation rate was observed with further increases of ρ(Fe-MnO_x). In addition, the degradation rate of AO7 decreased when ρ(AO7)₀ increased. The reaction of the Fe-MnO_x catalyst-activated PMS was conducted with the addition of one of two probe compounds to detect the generation of reactive oxygen species:ethylalcohol (EA) and tertbutylalcohol (TBA). The degradation rate of AO7 at 55 min was 79.40% by adding EA and 91.33% by adding TBA. Therefore, the oxygen species in the system were identified as mostly sulfate radicals and a small amount of hydroxyl radicals. The results of XRD and XPS indicated that the Fe-MnO_x catalyst consisted of Fe₂O₃, Mn₃O₄ and Mn₅O₈, in which the relative molar quantities of Fe³⁺, Mn²⁺, Mn⁴⁺, O²⁺ and surface hydroxyl oxygen were 20.49%, 26.46%, 5.60%,32.51% and 14.91%, respectively. The study indicated that Fe-MnO_x catalyst had a low metallic ion leaching, and good ability to activate PMS and degrade organic pollutants into radicals.