Aim: The aim of this study was to investigate the degradation of an azo dye, reactive red 198 (RR198), by ozone, H2O2/O3, and persulfate from aqueous solutions. Materials and Methods: The application of several advanced oxidation processes including single ozonation, O3/H2O2, and persulfate for degradation of RR198 at concentration of 200 mg/L was investigated. The effect of various parameters including pH, H2O2, persulfate doses, and temperature was studied on the degradation of RR198 from aqueous solutions. In addition, the effects of these processes on biodegradability of RR198 were evaluated. Results: The results showed that the degradation rate was increased by increasing H2O2 concentration. The optimum H2O2 concentration was obtained in the range of 0.03 mol/L at dye concentration of 200 mg/L. Alkaline pH, higher temperature, and persulfate dose (12 mM) were favored in dye and COD removal. Moreover, compared with ozone and peroxone, the persulfate oxidation could achieve a higher color and COD removal at the same reaction time. Persulfate has greater potential to improve the biodegradability of RR198 solution than ozone and ozone/H2O2 process. Biochemical oxygen demand/COD ratio of the dye solution treated by persulfate, ozone/H2O2, and ozone at reaction time 40 min was 0.73, 0.63, and 0.59, respectively. Conclusion: These findings show that oxidation by persulfate is a promising alternative for the treatment of RR198 containing solution as a recalcitrant pollutant.