Due to the climate change and large-scale human activities, especially the environmental changes caused by building thelarge hydropwoer projects such as the Three Gorges Reservoir and Gezhouba Hydropower Station, the flood series in the DongtingLake area has altered, which resulted in the non-stationary flood series distribution. Taking the Mituosi Station in the DongtingLake area as a case, This paper applied four inconsistent hydrological frequency calculation methods including the linear tendencyanalysis, non-linear tendency analysis, wavelet analysis and Hilbert-Huang transform to calculate the frequency distribution of theannual maximum peak discharge at the station, and made a merit-based comparative analysis. The results show that the mean val -ues of the annual maximum peak discharge series have declined significantly. The difference of the frequency curves calculated bythe four methods is relatively small in the past and current conditions while that of the prediction for the future is quite great. Afterthe calculation of preferred degree and comparative analysis, the results are optimal based on the nonlinear trend method. Fur -thermore, it finds out that there is significant difference in the frequency distribution of the annual maximum peak discharge underthe past, current and future conditions, which would directly affect the safety assessment of the embankments near the Mituosi sta -tion and regional flood control planning.