Based on the cobaltic ion (Co2+), the contrastive experiments on the activation of peroxomonosulfate (PMS) via combining transition metal irons like Cu2+, Mn2+, Ni2+, Zn2+ and Fe3 with UV were investigated, which was used to examine the competence of the different transition metal ions/UV processes to activate PMS. The results revealed that it was ineffective to combine Cu2+, Mn2+, Ni2+, Zn2+ and Fe3 with UV or PMS alone with the purpose of removing the target compound. However, the Co2+/PMS process was more effective for the degradation of the target compound. The competence of activating PMS in the Cu2+, Mn2+, Ni2+, Zn2+ and Fe3/UV processes was stronger than that in the Co2+/PMS/UV process. Besides, the Cu2+/UV, Mn2+/UV and Fe3/UV processes could activate more PMS than the Ni2+/UV and Zn2+/UV processes. The addition of radical scavengers, tert-butyl alcohol (TBA) and ethyl alcohol (EA), demonstrated that sulfate radicals (SO4-.) and a small amount of hydroxyl radicals (HO?) were the primary oxygen species in the Cu2+/PMS/UV, Mn2+/PMS/UV and Fe3/PMSUV processes. In these three processes, the degradation of AO7 was followed the pseudo-first-order kinetics, and the UV-vis absorption spectra of AO7 indicated that it was removed effectively. Moreover, the M/PMS/UV process has a wide range of application to degrade dyes.