Abstract: In this study, three reanalysis products (i.e. CRU, ERA-Interim and JRA-55) are evaluated using in situ measurements at 33 weather stations over the Three Gorges reservoir area for 1991-2006. The measurement variables include monthly air temperature and precipitation at all stations. Some approaches, including timing analysis, correlation analysis and percentage deviation, are utilized to quantify the relative performance of reanalysis data with respect to each variable. The results show that the monthly temperature from all reanalysis data are overall in better agreement with in situ observations compared with the precipitation. However, three types of data all underestimate the temperatures in each season, and the significant differences are seen in winter. As for precipitation, ERA-Interim data largely overestimate the overall precipitation in the Three Gorges reservoir area, and in winter, both ERA-Interim data and JRA-55 data show a marked underestimation of precipitation, with a deviation of about -40%. On the whole, at monthly scale, CRU is superior to others in air temperature and precipitation for the Three Gorges reservoir area. Based on the result, CRU was selected to analyze the characteristics of climate changes in the Three Gorges Reservoir before and after the impoundment by using trend analysis and ensemble empirical model decomposition (EEMD) After the impoundment, the significantly rising trend of the temperature in the Three Gorges reservoir area turns to a slight downtrend. No obvious changes are found in spring, summer and annual averaged precipitation. However, affected by the impoundment, autumn precipitation has notably increased and winter precipitation decreased. Moreover, strength of warming to the north of the Yangtze River like Chongqing and Beibei is greater than their adjacent regions. Impacts of impoundment on the spatial distribution of precipitation changes are not identical in different regions and seasons. In addition, the EEMD results indicates that quasi-periodic variations with about 2 to 3 years, 5 years and 7 to 8 years in both temperature and precipitation in the Three Gorges reservoir area. It also shows that the annual averaged temperature in this area undergoes slow trend in recent years, but may increase more obviously in future.