This paper has detected the trends and abrupt changes of climate changes in Lake Dongting basin in the past 40 years based on observed data of 22 meteorological stations. Lake Dongting basin had undergone a slow but steady increase of temperature since 1970s, but a significant increase with abrupt change has been detected since 1990s, especially in spring and winter;while in summer, the temeprelure has changed little. A positive and abrupt trend of precipitation in summer as well as its storm frequency has been well detected in 1990s;on the contrary, hardly has the storm density changed. The reference evapotranspiration has decreased steadily and obviously since 1960s;and in summer the decrease is of much more significance. The accelerated water circulation driven by global warming-up has brought the Lake Dongting basin more precipitation in summer, but the reference evapotranspiration has decreased at the same time,as is the main climatic contributor to the frequent floods in summer in 1990s