In this study, advanced treatment processes were constituted with Ozonation, Coagulation, Sand Filtration, GAC adsorption and Chlorination to reduce THMFP. Inappropriate ozone dosage in drinking water treatment process will increase THMFP, which will produce high concentration of THMs in chlorination. So ozone dosage must be carefully determined, considering pH, water temperature and concentration of organic pollutants in raw water. The results showed that 3ppm of ozone dosage was optimal, considering economic factors and noticable decreasement of THMFP, KMnO₄ demand and TOC. 92% of NH₃-N was removed by chlorination, but the other processes were not effective. In this process, removal efficiencies of organic pollutants, such as THMFP, UV254nm, KMnO₄ demand and TOC were 73.6%, 98.4%, 89.3% and 79.2%, respectively.