In this study, Fe3O4/Co3O4 composites were prepared and applied in the catalytic ozonation of sulfamethoxazole (SMX). Various parameters including initial solution pH, Fe3O4/Co3O4 composites dose, O3 dose and SMX concentration were investigated. Results showed that Fe3O4/Co3O4 composites could significantly improve the mineralization of SMX by catalytic ozonation system and a synergic effect between Fe3O4 and Co3O4 was observed. Only about 16% total organic carbon (TOC) could be removed in 60 min by single ozonation under the condition of 20 mg/L SMX, 6.0 mg/min O3, pH 5.1 and room temperature, While in the presence of 0.10 g/L Fe3O4/Co3O4 composites at the same conditions, 60% TOC removal were obtained by catalytic ozonation process. SMX could be degradation by O3 rapidly and the removal was not significantly affected by the changing parameters. However, those operating parameters exerted different effects on SMX mineralization. Furthermore, the generation of hydroxyl radicals (OH) and the utilization efficiency of O3 would increase with the addition of Fe3O4/Co3O4 composites. The quenching experiments indicated that OH might account for the enhancement of SMX mineralization and the mechanism of catalytic ozonation was proposed. Additionally, the intermediates were detected by using a high-performance liquid chromatography-mass spectrometry (LC-MS), from which some plausible transformation pathways were proposed.