Choosing the observed daily data from the Ziluoshan Stationin the Huaihe River Basin, this paper used the maximumlikelihood method to estimate Generalized Pareto (GP) distribution parameters for calculating the recurrence interval level and confidence interval with the Peak of Threshold (POT)approach. The goodness-of-fitting test show that the POT model canget a betterempirical sample point while enlarge the flood sample. The sensitive analyses of different time duration flood data show that the time duration has a significant impact on the recurrence interval calculation.