This study aimed to investigate the catalytic performance of Fe3O4/ZnO in the ozonation of 1-hexyl-3-methyl imidazolium bromide ([HMIM]Br). The Fe3O4/ZnO composite was prepared by a quick and convenient two-step coprecipitation method, and the optimum mass ratio of Fe3O4:ZnO was determined as 1:8. The structure, surface morphology, and chemical composition of the Fe3O4/ZnO composites were studied by characterization methods. The degradation efficiency of [HMIM]Br reached 96% in 5 min in catalytic ozonation with the Fe3O4/ZnO composite, an increase of 20% compared with ozonation alone. Moreover, the pseudo-first-order rate constant was 1.5 times higher than ozonation alone. With the increase in the catalyst dosage, the degradation efficiency of [HMIM]Br first improved and then decreased, and the optimum dosage was 0.25 g/L. The increase in pH value and the introduction of Cu2+ effectively promoted the catalytic ozonation of [HMIM]Br with Fe3O4/ZnO, while the reducing inorganic ions inhibited the ozonation reaction. Different water matrices had little influence on the catalytic performance of Fe3O4/ZnO. Radical scavenging and EPR experiments showed that hydroxyl radicals (•OH), superoxide radicals (O2•-) and singlet oxygen (1O2) were the main active species in this system. Meanwhile, product identification showed that the degradation of [HMIM]Br mainly included hydroxylation, imidazole ring cleavage and bond cleavage. Toxicity prediction illustrated that the catalytic ozonation of [HMIM]Br could effectively reduce its toxicity. The efficiency, toxicity, reusability, and stability experiments suggested that the developed catalyst, Fe3O4/ZnO composite, had promising prospects in catalytic ozonation.