Advanced oxidation methods which were used for degradation of pollutants in wastewater have attracted more and more attention in recent years. In this article, an S-modified CoFe2O4 nanoparticle catalyst was prepared with CoFe2O4 precursor synthesized by co-precipitation method. The catalyst was characterized by BET surface area and porosity analyzer, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR) and vibrating sample magnetometer (VSM). Results indicate that the synthesized catalysts were nanoparticles with a high specific surface area of 49.8 m2/g and well magnetic property. To evaluate the degradation effect of different samples of catalysts, a series of catalytic reactions have been conducted to degrade the Acid Orange II (AOII) aqueous solution. Under the conditions of 0.1 g/L S-CoFe2O4, 3 mM H2O2 and 0.1 g/L NaHCO3, almost up to 99% degradation of 50 mg/L AOII solution was achieved only within 15 min, and about 40% of total organic carbon (TOC) removal during 30 min reaction. Except for that, the reaction mechanism was investigated, especially for the effects of introducing sulfur and NaHCO3 into the reaction system as well as the amount of cobalt and iron leaching. For used catalyst, BET, XRD and energy dispersive X-ray spectroscopy (EDS) were also measured to further discuss the stability and durability.