This study evaluated the beneficial effects on the coagulation process of combining coagulants with Fe and Al in the removal of turbidity and DOC (dissolved organic carbon), and proposed conditions for proper operation of a coagulation process. In addition, the floc characteristics and sludge dewater ability were evaluated. Blended coagulants were more effective than single coagulants at lower concentrations in water purification. The optimal blended ratio for the removal of DOC was 1.45 mM as Al/mM as Fe. Also, blended coagulants were less affected than single coagulants by pH, temperature, and rapid mixing intensity. Based on the results of the change in the apparent molecular weight distribution (AMWD) of DOC in raw and treated water by coagulation, low molecular weight organic matters were removed by 40.7% for the blended coagulant (1.45 mM as Al/mM as Fe). Blended coagulants formed larger flocs than single coagulants did. At pH 6.0, floc strength and sludge dewaterablity were both improved.