Catalytic wet air oxidation (CWAO) was investigated in laboratory-scale experiments for the treatment of o-chlorophenol in wastewater. Experimental results showed that wet air oxidation (WAO) process in the absence of catalyst was also effective for o-chlorophenol in wastewater treatment. Up to 80% of the initial CODCr was removed by wet air oxidation at 270degreesC with twice amount of the required stoichiometric oxygen supply. At temperature of 150degreesC, the removal rate of CODCr was only 30%. Fe-2(SO4)(3), CuSO4, Cu(NO3)(2) and MnSO4 exhibited high catalytic activity. Higher removal rate of CODCr was obtained by CWAO. More than 96% of the initial CODCr was removed at 270degreesC and 84.6%-93.6% of the initial CODCr was removed at 150degreesC. Mixed catalysts had better catalytic activity for the degradation of o-chlorophenol in wastewater.