|In this study, in order to estimate the drought flow by L-moment method, the rainfall of a day at the six observation station in the river basin and the neighborhood in Holchun was used. The weight value about area ratio was analysis and to do the initial input data of L-moment method, the date was analysed in the way of return period-exceed probability-duration. At the result of estimating the hydrological homogeneity, at the observation stations, in the use of parameter by L-moment method, less than I was presented in the heterogeneity measure H. Therefore, each observation station was thought to have the hydrological homogeneity, and at the result of agreement of the data the extreme minimum in the data Di, was not present, so it was presented, so it was no observation station having possibility of the falseness in data itself. At the result of the analysis in the goodness of fit measure Z, to choose the optimal probability distribution in each duration, the difference was presented in the optimal distribution type every 15 month of duration. And the optimal distribution type GN was presented in the continual drought in relatively short duration, 4, 6, 9, 12 months at the agreement with IZI≤1.64 order. And the optimal distribution type GL was presented at the duration of more than 15 months.