Abstract: The applicability of design flood hydrograph as a basis of the design of reserviors safety withstanding flood has been examined by using statistical experiment. This examination is based on the stochastic flood model which was developed for the hydrological design of Zhi Ping Pu reservior. The results have shown that design flood hydrograph may lead the actual criterion of reservior safety withstanding flood to deviate seriously from the specified one. The main factor which may have a strong impact on such a deviation is the sample errors of certain flood volumes in a flood hydrograph. The prerequisite of the applicability of design flood hydrograph is also discussed in this paper.