A bimetallic catalyst, Co-Mn oxide (CoMnO_x), was prepared via sol-gel method to activate peroxymonosulfate (PMS) to produce oxygen species for degradation of acid orange 7 (AO7). The effects of CoMnO_x dosage, PMS dosage, AO7 dosage, and initial pH on removal efficiency of AO7 were investigated. The experimental results indicated that high CoMnO_x and PMS dosage had a prominent impact on the degradation of AO7, weak acid initial pH condition enhance the degradation efficiency, but the increasing of AO7 dosage had anopposite effect, the degradation rate of AO7 could reach 95.28% under the best reaction condition. By adding different radical scavengers:ethylalcohol (EA) and tertbutylalcohol (TBA), the oxygen species were identified as sulfate radical (SO₄^-·) and hydroxyl radical (OH·)in which SO₄^-·made the predominant contribution. The catalyst was characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD). The results showed that the major component of the CoMnO_x catalyst was MnCo₂O₄, in which the mole percentage of Co²⁺, Co³⁺, Mn²⁺, Mn³⁺, lattice oxygen and surface hydroxyl oxygen were 27.94%, 6.16%, 11.42%, 19.99%, 25.99%, 8.68%.