Abstract:Using daily NCEP/NCAR reanalysis dataset and the historical Meiyu feature index etc., the causes of abnormal rainfall and its large scale circulation during 20 07 Meiyu season are analyzed in order to better understand the evolvement charac teristics of persistent rainfall and its atmospheric circulation on Jiang Huai Meiyu, and to discuss technical approaches of mid range forecast. The results s how that the stability of the western Pacific subtropical high located in the so uth more persistently than normal in middle late July during Meiyu season plays a crucial role in the temporal and spatial characteristics during 2007 Meiyu pe riod. The frequent appearance of blocking high and abnormal strong subtropical monsoon surge provide favored dyna mic, thermodynamic and moisture factors affecti ng maintenance and intensification of Meiyu front. The activity of “Iran type” south Asia High and upper low level coupling dynamic action of subtropical jet in East Asia not only create favorable vertical circulation structure for pe rsistent heavy rainfall but also restrain northward movement of subtropical high . At last, the keys of mid range forecast are summarized on the basis of these results.