Abstract-This paper describes the degradation of red anthraquinone dyes (alizarin, alizarin S and alizarin complexone) with initial concentration of 100 ppm in aqueous solution by ozone oxidation. The results of UV/VIS and FTIR spectra showed that the anthraquinone structures, nitrogen linkages and amino groups of anthraquinone dyes were broken after the direct ozone reaction. Almost complete color removal was obtained through ozonation within about 70, 18 and 18 min, reaction time for alizarin, alizarin S and alizarin complexone, respectively. The analysis of residuals by FTIR indicated that the alizarin primary degradation products were some organic compounds (e.g., aromatic groups, carbonate esther) and CO 3 2-(due to the dye mineralization). Alizarin S degradation products exhibited IR absorption bands at 1717, 1623, 1387, 1105 and 1045 cm -1 , attributed to >C=O (carbonyl), >C=C< (alkenes), -C-C-C (alkanes), SO 4 2-and -C-O-C-groups respectively. Approximately 90% of alizarin can be removed from water streams with the present methodology; followed by approximately 80% removal of complexone and 70% removal of alizarin S.