Abstract: The synoptic seasonal characteristics of rainfall are studied by means of the analysis of EOF (Empirical Orthogonal Fuction) of the daily amounts of precipitation field in Henan Province during the rainy season, usually known as the flood season. The precipitation in the flood season is possessed of sameness in Henan which is hinterland of Huanghe-Huaihe area. The main flood season occurs after the Meiyu period over Changjing-Huaihe River Valley and is properly referred to as Shuxun period (flood season in the dog-days). The oscillation of rainfall in Henan shows out of phase in the direction from north to south and from west to east obviously during the Shuxun period. Especially it is important property of monsoon climate over East Asia that the monsoon rain belt jumps from south of Shahe River to the littoral area and to the north of Huanghe River from Slight Heat (11th solar term) to Great Heat (12th solar term). This expresses that after the end of the meiyu period the main rain belt in the East Chain does not turn immediately to the north arear of Huanghe, but gradually, by stages. The analysis and reasearch of the precipitation climate in the Shuxun period are helpful to deepen our knowledge of the monsson motion in the eastern Asia.