Perovskite oxides are considered as promising catalysts in activating peroxymonosulfate (PMS) for environmental remediation, but the intrinsic properties that govern the activity of perovskites are ambiguous. Herein, a series of perovskite-type oxides La2MeO4 (LMe, where Me = Co, Mn, Cu, and Fe) were reported to activate PMS for improving organic pollutant degradation, while the LCo/PMS system showed impressive performance, achieving over 90 % removal of organic contaminants (dyes and antibiotics) under the optimized conditions of 0.05 g/L catalyst and 0.50 mM PMS. Experiments and characterizations verified a good linear correlation between the catalytic activity and effective magnetic moment (μeff) of catalysts, underlining the key role of the spin state of the metal center in governing the intrinsic activity. Additionally, two stages of oxidation pathways were evidenced to be involved in the reaction: i) high-valent cobalt-oxo species (i.e., Co(IV)) were produced from the surface reactive complexes catalyst-PMS*, afterwards ii) a portion of superoxide radicals (O2•−) were formed via the PMS reaction with Co(IV). Overall, these findings provide new insights into the mechanism of the perovskite-activated PMS system for efficient water remediation.