Phenol is a major environmental contaminant produced by various industries. In this study, phenol degradation was achieved using ozone treatment. The main parameter affecting the phenol degradation, i. e., ozone concentration, H 2 O 2 /phenol molar ratio and reaction time, were studied using statistical design of experiments to optimize the phenol degradation in terms of studied parameters. The results of the statistical design indicated that the ozone oxidation can be used for phenol degradation reaching high efficiency of 100 %. It was indicated that there is not only one condition at which the complete degradation can be carried out but also several design points lead to the same results. For instance, the complete degradation can be achieved at six hours reaction time, 0.03 H 2 O 2 /phenol molar ratio, and 10 g/m 3 ozone concentration.