This study was compared with water treatment characteristics that is water treatment system of 2-stage biofilter and advanced water treatment system of sandfilter-O3/GAC. Influent water was used grit chamber effluent water of K water treatment plant in Busan. The experiments was operated pilot-plant scale for 100 days. Operating conditions were temperature 20∼29℃ and pH 6.9∼7.9. Optimal EBCT was 30 min, when EBCT changes was 10 to 40 min on biofilter process. The pre-treatment efficiency of biofilter was turbidity 90.0%, color 91.2%, KMnO4 consumption 81.1%, COD(Mn) 91.5%, NH4+-N 92.2%, UV254 71.0%, DOC 54.5%. The comparative analysis on water treatment characteristics was made between 2-stage biofilter and sandfilter-O3/GAC. As a result, 2-stage biofilter was identified about 1∼5% higher efficiency in terms of turbidity, KMnO4 comsumption, NH4+-N and UV254. In addition, 2-stage biofilter was proven more economical because of saving 66% of plant site and without using coagulants.