The degradation performance of atrazine by peroxymonosulfate (PMS) activated by CoFe2O4 nanoparticles (NPs) in heterogeneous catalytic process was studied in our study. In this work, first of all, influences of vital parameters (i.e., CoFe2O4 dose, PMS dose, initial pH, co-existing anion, and atrazine (ATZ) concentration) on ATZ removal were investigated systematically. The removal of ATZ (>99%) and first order reaction kinetic rate constant (K-obs = 0.181 min(-1)) were achieved after 30 min reaction with 0.4 g/L CoFe2O4, 0.8 mM PMS, and 10 mg/L ATZ at initial pH 6.3. In contrast, only 10% and 6% ATZ removal were achieved with PMS and CoFe2O4, respectively, verifying the excellent performance in the CoFe2O4/PMS system. In addition, reusability of the CoFe2O4 NPs was investigated after five successive runs. Radical quenching experiments were done and SO4 center dot- was identified as the main radical species. The fresh and used CoFe2O4 NPs were characterized via SEM, EDS, XRD and XPS techniques. What's more, the possible degradation intermediates in CoFe2O4/PMS system were determined by ultrahigh performance liquid chromatograph-mass spectrometry. Activated sludge inhibition experiment was carried out to evaluate the variation of toxicity of the ATZ and its degradation intermediates in the oxidation process. Based on the identified products, the degradation pathway of ATZ in CoFe2O4/PMS system was put forward. Finally, the believable reaction mechanism of CoFe2O4/PMS system was proposed according to the comprehensive analysis.