This paper presents the flow chart of a new method for base flow hydrograph separation based on the Horton infil- tration capacity curve.Five watersheds located in different climatic areas are selected as study cases.The computation re- suits are compared with the other separation methods based on the nonlinear reservoir assumption and the digital filter.It is found that the inflow and outflow of the base flow hydrographs separated by the new method has physical means and expla- nation in accordance with the hydrological reality,and is more rational than those of the other two methods.The proposed method is very useful for unit hydrograph analysis and for the study of the rainfall runoff relationship.