Based on the precipitation and temperature data at National Climate Centre 723 stations, the JRA25 and NCEP/NCAR I reanalysis data sets and the NOAA Climate Prediction Centre extended reconstructed SST data, using methods of linear trend, dynamical diagnosis, correlation analysis and wavelet analysis, the climate characteristics and variation features of seven great river valleys (SGRV) in July 2011 were researched, and the mechanism of precipitation anomalies of the Yangtze River Valley (YRV) during the dominant flood season was revealed. Results indicated that the precipitations of SGRV were overall less in July 2011, however, the precipitation of YRV was far less than normal; meanwhile, the temperatures of SGRV were characterized by continued climate warming, especially for Songhua River Valley. The linear trend of precipitation changing showed that Zhujiang River Valley and YRV were in a linearly increased trend, Huaihe River Valley maintained an unchanged condition, and Liaohe, Haihe, Huanghe and Songhua River Valleys where in a linearly decreased trend. In addition to the obvious interannual variability, the decadal changes of precipitation in YRV, Huaihe, Haihe and Huanghe River Valleys were also obvious. The main causes for the belownormal precipitation of YRV in July 2011 were as follows: The atmospheric responses to external forcing of equatorial MiddleEastern Pacific were the same as those to La Nina pattern; the subtropical high was abnormal and the East Asian southerly wind circulation intensity index (IES) was weak; besides, the water vapor budget had a deficit and the precipitation efficiency was low.