This study aimed to investigate the degradation of Congo red and Rhodamine B dyes in synthetic wastewater by ozonation and study the parameters that influence the efficiencies of color removal such as concentration of pollutants, gas flow rate, time of reaction, and the pH of solution. Congo red dye and Rhodamine B dye were selected as model pollutants. ozonation process of these dyes was carried out in a continuous reactor with a diameter of 8cm and length of 25cm. It was observed that over 85% of Congo red and 95% of Rhodamine B could be removed at 90 min for both dyes. and when using the H2O2 (0.5, 1, 1.5)ml for Rhodamine B and Cong Red at 90 min the decolorization efficiency in natural pH was 93%,95%,96%, 84%,89%, and 94% respectively. When used the packing the decolorization efficiency changed from 77% to 82% for Rhodamine B and from 53% to 63 %for Congo Red. Higher color removal could be achieved when ozonation was carried out in an alkaline condition (pH 10) for Congo Red and an acidic condition (pH 1.5) for Rhodamine B. The ozonation of dyes was dominant at room temperature and atmospheric pressure.