On the subject of river bed water in Seomjin river, it had accomplished the verifying experiment of membranefiltration pilot plant for evaluating the applicability of its process throughout the prediction of membrane fouling asa function of the pore size of membrane and the determination of optimum coagulant dosage. On the result of the experimentfor the evaluation of the membrane fouling as a function of the pore size, a increasing rate of irreversible resistanceof membrane pore size 0.1 μm and 0.01 μm was measured each 0.44 × 10¹²/m² and 0.42 × 10¹²/m², respectively. And onthe result of Flux-test, it showed that the optimum coagulant dosage was measured lower than the it of the Jar-test. Theresult to be operated in a condition of a permeate flux 1.0∼1.5 m³/m²⋅day without coagulation and a permeate flux 1.0∼2.0 m³/m²⋅day with coagulation was maintained at stable trans-membrane pressure (TMP) value for 6 months up to.Therefore it showed that the stable operation without the coagulation was possible on permeate flux 1.0∼1.5 m³/m²⋅day in the operation of membrane filtration process.