Activated carbon (AC) catalyst was successfully improved activity for the degradation of Reactive blue 49 dye (RB 49) in catalytic ozonation system. The degradation of the RB 49 dye was visualized by UV-Visible spectroscopy. As the RB 49 degradation kinetics were investigated by different initial parameters, initial RB 49 concentrations, AC catalyst loading, H 2 O 2 dosage and additives. The degradation efficiency of AC catalytic ozonation towards RB 49 was found to be 95% when compared to 45% using pure ozone. The concentration of AC catalyst ranged from 0, 0.01, 0.05 and 0.1 g/L. We found that the maximum pseudo first and second order rate constant were 0.186 min -1 and 1.416 L.mg -1 min -1 for 0.05 g/L AC. The results showed that the optimum of AC concentration in system was 0.05 g/L. In addition, this research studied the effect of auxiliary chemicals such as NaCl, Na 2 CO 3 , Na 2 SO 4 and H 2 O 2 upon dye degradation in AC catalytic ozonation system.