Dongting Lake region is known as the land of fish and rice, and world famous Wetland Nature Reserve. Global warming and the frequent occurrences of extreme weather and climate events are inevitably affecting the water resources of the region. Utilizable precipitation is a kind of water resource that can be utilized in actual use and its changes directly affect the agricultural production, wetland protection and other aspects of the region. Based on the regional mean monthly temperature and precipitation series from 1910 to 2013 constructed by the all 21 meteorological stations in Dongting Lake region, the evaporation was calculated by Takahashi's equation and its reliability was verified, then utilizable precipitation was obtained by the relationship of water balance. After that, the statistical methods were used to analyze the changes of utilizable precipitation series. The results indicated that utilizable precipitation of Dongting Lake region concentrated from Mar. to Jun., accounting for 60.0% of the whole year. Annual utilizable precipitation of Dongting Lake region over the past 104 years had no significant linear change trend but had obvious inter-decadal fluctuation with a periodic oscillation of 20~25 a. The changes of utilizable precipitation had seasonal differences, it had ascending trends in winter and summer, but descending in autumn and no significant change in spring. However, the linear trend of precipitation in each season did not pass the significance test and inter-decadal fluctuation was the main characteristics of change. The abrupt change test showed that the annual utilizable precipitation over recent 100 years had a abrupt rising jump and the same phenomenon in winter and summer, and it showed that although the utilizable precipitation in the year and the above seasons was characterized by the inter-decadal variability, there were also sudden increases in a certain period. The results of Morlet wavelet transformation showed that the annual and seasonal utilizable precipitation series had several periodic oscillations of multi time scales over Dongting Lake region and all have experienced 10~13 shifts of wet or dry periods , and each wet or dry period existed inter-annual fluctuations. This article aims to provide an important theoretical basis for future agricultural production, flood prevention and drought resistance in this region, and provide theoretical guidances for the development of climate change strategy.