The impact of climate change on floods and droughts in Huaihe River Basin is studied using a coupled land-surface hydrology model and continuous wavelet transform technique. Observed temperature in the basin has increased by approximately 0.228 °C per decade since 1951. Observed precipitation and simulated and observed streamflows are used to grade flood and drought events. Two composite grading indices derived from the three series using different weight values are defined for reducing uncertainties caused by errors of observation and simulation and the effect of human activity on observed streamflow. The frequency of flood and drought events is quantified using the Morlet wavelet transform and compared with the trend of average temperature to test for any relationship between climate change and flood/drought frequency. This study shows that flood and drought events have occurred more frequently since the 1980s. The trend of flood and drought events is positively related to climate warming with a coefficient of determination of 0.88 in the Huaihe River Basin.