Landfill leachate is classified as special wastewater because it contains a large amount of hazardous materials that can lead to the pollution of surface water, generating polluted water with landfill leachate (PWLL) with high organic load. This study investigated the treatment of PWLL by peroxymonosulfate (PMS)/O3/UV process. The effects of several operating parameters such as pH, reaction time, O3 and PMS dosage were investigated in detail. The results showed that PMS/O3/UV removed total organic carbon (TOC) (74%), color (98%), ammonia (93%), chemical oxygen demand (COD) (81%), and biochemical oxygen demand (BOD) (69%) in 75 min at optimal conditions (pH=7, PMS=5mM, O3=1.7 mg/min). According to the results, O3 and UV can well activate PMS and promote the ability of the process to remove TOC from PWLL. Adding ferrous ion to PMS/O3/UV increased the TOC removal efficiency (77%), but cobalt ions had no significant effect on the TOC removal. The elimination of TOC by the PMS/O3/UV process follows pseudo-first-order kinetic model with the reaction rate constant of 0.0203 min?1. Compared to peroxone/ UV, PMS/O3/UV showed high yield in TOC, COD, color and ammonia removal. Thus the PMS/O3/UV process can be a new approach for treatment of polluted water in low volume.