Estimations of the unit pollutant loading from point source have been conducted oftenly in korea and the results were used to calculate the amounts of pollutant from the point source. But survey for the estimation of the unit pollutant loading from non-point source were not performed sufficiently because of the variation of pollutant effluent factors such as the methods of fertilizing, the patterns of irrigation, rainfall occuring, land use. The stream flowrate measurement and soil column test was carried out to develop the estimation methods of the unit pollutant loading rate discharged from the non-point source. And it seemed that the unit pollutant loading discharged from the non-point source mainly depends on the characteristics of rainfall and amount of flowrate from the watershed. The unit BOD loading rate calculated by this methods were shown as 3.78㎏/㎡· day in forest area, 6.33㎏/㎡·day in farm dry field and 8.60㎏/㎡ ·day in rice paddy area.