In this study, average rainfall of basin was estimated and compared with that obtained from Biseulsan dual polarization RADAR. And the runoffs are estimated using Vflo distribution model for Habcheon reservoir basin and Huicheon basin. In the rainfall estimation using dual polarization RADAR, the rainfall was estimated by using the specific phase difference and differential reflectivity of dual polarization RADAR variables. As a result, for all events rainfall estimation using dual polarization RADAR has the closest value to the gauge rainfall in terms of the peak rainfall and total rainfall. Also, runoff simulation results from dual polarization RADAR show the better results. It is concluded that the method using dual polarization radar can improve the accuracy more than a single polarization radar using only horizontal reflectivity.