Photosensitive Co3O4 nanorods were synthesized by a facile one-pot hydrothermal method followed by calcination at different temperatures. The crystal structure, morphology, thermal and textural properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and nitrogen sorption isotherms. The performances of the samples in catalytic activation of peroxymonosulfate (PMS) for phenol degradation were found to be dependent on the calcination temperature. Electron paramagnetic resonance (EPR) and classical quenching tests were applied to investigate the mechanism of PMS activation and phenol oxidation. At a proper amount of PMS loading, a synergistic effect of photo- and chemical-oxidation was observed. This study suggested that utilization of sunlight can greatly reduce the chemical consumption in environmental remediation thus providing a cost-effective and more environmentally friendly approach for water treatment.