In this study, catalytic wet air oxidation of wastewater that contains organic matter (phenol) is investigated in a laboratory scale trickle-bed reactor. The aim of this project is to determine the optimum operating conditions for the reaction of phenol in the wastewater with oxygen using a catalyst. For this purpose, the effects of temperature, gas flow rate, liquid space velocity and initial concentration of phenol on the conversion of phenol at constant pressure and the effect of pressure on the conversion of phenol at constant temperature are investigated. An industrial copper chromite catalyst was used in the experimental studies. It is seen from the experimental results, conversion of phenol increases with increasing temperature, pressure, gas flow rate and liquid space velocity; and also, it is seen that conversion of phenol decreases with increasing initial concentration of phenol. The conversion of phenol reaches at 130?C and 4 bar to 40%. It was also found that, 3 ppm copper amount was determined from the exit stream of the reactor. This result shows that cupper placed in the structure of the catalyst, mixes with the liquid stream during the reaction.