A magnetic composite CuFe2O4/diatomite (CFD) was prepared by citric acid assisted sol-gel method. The microstructure and elemental valence of the materials were analyzed by SEM, XRD, FTIR and XPS, and the effects of different oxidation systems, mass concentration of CFD, mass concentration of PMS, initial pH of solution, reaction temperature and anion type on the degradation of AO7 by CFD system were discussed. The results show that the spherical CuFe2O4 particles on CFD can be dispersed on diatomite, which reduces the agglomeration of pure CuFe2O4, and the valence cycles among the surface hydroxyl group, Fe3+/Fe2+ and Cu2+/Cu+ on CFD composite are involved in the activation of PMS. Under the optimal conditions of 0.5 g/L mass concentration of CFD, 0.3 g/L mass concentration of PMS, 50 mg/L mass concentration of AO7 and 30 ℃ reaction temperature, the degradation rate of AO7 in 60 min was 96.88%. The degradation process of AO7 in CFD+PMS system was in line with the quasi-first-order kinetic model. Compared with pure CuFe2O4+PMS system, the degradation rate constant of AO7 is increased by 1.98 times. The single factor test results show that the pH range of CFD+PMS system is wide (5~11) and the activation energy is low (Ea=31.77 kJ/mol). The quenching test showed that the main active substances in the degradation process were 1O2 and ?O2-, and SO4-? and ?OH were also produced.