Perfluorooctanoic acid (PFOA) was efficiently decomposed at Ti/SnO2-Sb anode via peroxymonosulfate (PMS) activation. PFOA degradation followed both pseudo-zero-order (0-30 min) and pseudo-first-order (30-120 min) kinetics. The pseudo-first-order kinetics constant could increase to 0.0484 min-1 (3.84 times higher than that without PMS) during 30-120 min electrolysis. The inhibited performance in radical scavengers implied both sulfate radical (SO4•-) and hydroxyl radical (•OH) contributed to PFOA degradation. The •OH quantitative detection experiments demonstrated that SO4•- formed from PMS activation could promote •OH generation (from 0.12 mM to 0.24 mM). Electron spin resonance (ESR) tests further proved that SO4•- and •OH were generated during PFOA degradation. According to linear sweep voltammetry (LSV) analyses, the oxygen evolution potential (OEP) value of Ti/SnO2-Sb electrode increased from 1.59 V to 1.72 V (vs SCE) via PMS addition, indicating the inhibited oxygen evolution which was beneficial for the reactive species formation (i.e. •OH, SO4•-). On the basis of intermediates verification and mass balance of carbon and fluorine, PFOA was proposed to be oxidized into short-chain perfluorocarboxylic acids mainly by •OH and SO4•-.