Abstract: The longitude location change characteristic of the East Asia Westerly Jet (EAWJ) core at the upper troposphere during meiyu period and its impacts on the spatial distribution of precipitation in the middle-lower reaches of the Yangtze River valley are investigated by using the 40 year's NCEP/NCAR reanalysis mean pentad data and observed daily precipitation data from 1958 to 1997. The results show that there are two areas, where the 200 hPa East Asia westerly jet center appears frequently during meiyu periods: one is located over the western Pacific and the other over the Asian continent. During the meiyu period, the intensity of the westerly jet over Asian continent weakens and the core of the westerly jet over western Pacific splits up and its intensity reduces, and disappears after the end of meiyu, which is the main characteristic of the longitude location change of the 200 hPa westerly jet over East Asian. The change in the location and intensity of the westerly jet is not only associated with the start and end of meiyu period, but also with the spatial distribution and intensity of precipitation in the middle-lower reaches of the Yangtze River valley. The further analysis suggests that when the westerly jet core at upper troposphere is located over the western Pacific, and coupled with an 850 hPa southwesterly jet, the heavy precipitation occurs in the lower reaches of the Yangtze River valley, where the convergence is strong and the water vapor supply sufficient. While the 200 hPa westerly jet core is located over the East Asian continent, and not coupled with an 850 hPa southwesterly jet, only the weaker precipitation occurs in the middle and lower reaches. Therefore, the longitude location changes of the East Asian westerly jet core play important roles in determining the upper-low level circulation structure and the spatial distribution of heavy precipitation in the middle and lower reaches of the Yangtze River valley during the meiyu period.