Peroxymonosulfate-based advanced oxidation process (PMS-AOPs) is one of most effective approaches for eliminating emerging organic pollutants (EOPs). To develop high-performance and stable PMS activators is the key to the further development of PMS-AOPs. Cobalt-based catalysts have been proved to be the excellent PMS activators. Here, cobalt bismuth oxide (Bi 7.53 Co 0.47 O 11.92 ) prepared by facile one-step calcination method was employed as the new PMS activator. As expected, diclofenac (DCF), one kind of EOPs, were quickly decomposed and even mineralization by the Bi 7.53 Co 0.47 O 11.92 activated PMS system. Within 10 min of reaction, 100% degradation efficiency and 82.1% mineralization rate were achieved. The toxicity of degraded products was assessed to be much lower than pristine DCF. Moreover, six-cycle experiments verified the good reusability of Bi 7.53 Co 0.47 O 11.92 . This work contributes to develop new stable and high-efficiency PMS heterogeneous activators, being beneficial to build high-performance PMS-AOPs for EOPs treatment. • Cobalt bismuth oxide with stable surface Co active site was synthesized. • Efficient mineralization and detoxification of DCF was achieved. • The stable reusability of cobalt bismuth oxide in activating PMS was determined. • Superoxide radicals were mainly responsible for the quick decomposition of DCF.