We have investigated ultraviolet (UV) irradiation combined with manganese ore (MO) catalyzed ozonation of 4-cholorophenol (4-CP) in aqueous solution. The preliminary results showed UV irradiation and MO had a strong synergetic catalytic effect on ozonation. We also studied the effect of UV lamp power, MO dosage, O3 dosage, initial 4-CP concentration, pH value and temperature. The results showed that high pressure mercury lamp (HPML) was more favorable for the degradation of 4-CP than low pressure mercury lamp (LPML). The optimal MO and O3 dosages were 2 g/L and 2 g/h respectively. When the 4-CP concentration was over 15 mg/L, the decrease of degradation efficiency accelerated. The acid condition was favorable for the degradation of 4-CP by UV/MO/O3. The reaction temperature could not be over 50°C. Through the mechanism discussion, we found that Mn2 +  was the most important species to catalyze the ozonation. In addition, UV irradiation could also accelerate the degradation by promoting the production of ∙OH.