Abstract:There are several similar characteristics in Meiyu period of 2003 and 2006. For example, the date of beginning and ending of Meiyu was consistent in above two years, the subtropical high ridge of Meiyu period of the two years also oscillated between 15°N and 27°N, and the heavy rainstorm during Meiyu period of the two year concentrated in Huaihe valley, Hongze lake and Lixiahe area of Jiangsu. But the total precipitation of Meiyu period in 2003 was more than that in 2006. The synoptic situation and conditions of thermodynamics and dynamics wh ich accompanied with heavy rainstorm during Meiyu period of 2003 and 2006 in Jia nghuai valley of Jiangsu are analyzed in details by using the T213 analysis data and composite average method. The results show that Meiyu front of 2003 is stro nger. In addition, the stable moisture transportation, overlappingcenter of converge nce and vorticity and vigorous ascending stream in 2003 were also favorable co nditions for the Meiyu. The number of heavy rainstorm day caused by strong convect ive system in 2006 was more than in 2003. The results also indicate that the rainfall amount in the period of Meiyu is proportional to the increment in the phys ical quantity.