In order to explore the trend of environmental changes under the snowmelt flood basin, the annual snowmelt flood sequence of the Ken Swart hydrologic station in the upper Manas River Basin was used as an example to test the interannual variation of peak volume by the Pettitt method and the Lee-Heghinian method. The mutation phenomenon was explored by R/S method, and the obtained mutation points divided the flood process into two stages. The weighted moving average method and Mann-Kendall method were used to analyze the trend of flood time series. The results showed that under the human activities and climate change, the flood signature sequence of the Manas River Basin has undergone moderate variation during 1957-2014, and the amplitude of the pre-mutation sequence is more obvious, while the overall change after the mutation point is decreasing but not significantly.