Abstract: In July 2007, a series of extreme precipitation events occurred over the middle and eastern parts of China, which caused the devastating flooding and considerable infrastructure damage and swept off many people. Based on the particle dispersion transport model FLEXPART, which is driven by the meteorological fields provided by the NCEP/NCAR analysis data and the outputs of the Weather Research and Forecasting (WRF) Model respectively, a very large number of particles (air parcels) trajectories were tracked backward. It initialized in a dense threedimensional grid array located over the extreme rainfall region and was followed by determining the transport pathways of the moisture according to the precipitation during the event. As well the possible evaporative sources of the precipitation falling over the eastern part of China and their quantitative contributions were investigated. The ten days backtracking analysis results show that this event was initially related with the transport of subtropical continental and tropical ocean moisture. During the process of transport, every air parcel might experience several periods of evaporationprecipitation in which it was significantly influenced by the combined action of the strong orographic enhancement of the Tibetan Plateau and the barrier of subtropical high pressure. Although the evaporation source was distributed over large parts of the areas, the major contribution to the precipitation is over the subtropical continent, including especially the Indian Peninsula, Myanmar and Sichuan and Yunnan Provinces over the southwestern part of China (approximately 40%). This indicates that the abnormal soil moisture over the upstream areas provides with a good indication for the extreme precipitation.