By use of daily data of plums rain during plums flood periods from 1954 to 2008,the dates of beginning and ending,lasting day,total rainfalls of the Mei-Yu periods were analysed.And the results show that the dates of beginning and ending and total rainfalls of the Mei-Yu period featured annual variations,and lasting day,synoptic circumstances and total rainfalls of the Mei-Yu period have some corresponding relations.The focus is on synoptic circumstances of for-mer 24 hours before the appearing of heavy rai...