Based on daily rainfall data and NCEP/NCAR 1°×1° FNL data during the Jianghuai Meiyu period in the summer of 2011,the main influential system and its circulation characteristics of the Meiyu were analyzed.It was found the features of the blocking situation in the 2011 Meiyu period and those during other typical Meiyu times were different:High-latitude blocking had mobility and the main cold air in the 2011 Meiyu period was from the polar vortex splitting southward caused by development of the middle-high latitude circulation.Moreover,the cutting trough caused by the weak resistance situation in middle and high latitude provided the dynamic condition for the Meiyu.It was also found the development of the Meiyu rainstorm was associated with the oscillation of the Northwest Pacific subtropical high ridge.In addition,the influence mechanism of Meiyu front system,the jets and the sub-circulation triggered by them as well as the dry cold air's intrusion on the rainstorm were discussed.