Abstract: Based on daily radiosounding data during the period of May-Augus at 850 hPa, the mean merid-ional water vapor transportations at different latitudes were computed over the East of China and a spectral analysis was carried out. It is found that the water vapour trans portations in summer exhibit different oscillation with the latitudes, closly related to the seasonal northward movement of the rainfall belt over our country, over the South China Sea-Southern China, the 40-50 day and 4 day oscillations prevail in the water vapour transportation; over Changjiang River reaches, the about 80 and 8 day periods are dominant while over Northern China the 5 day oscillation is signifcant By using composite method, it is also found that the rainfall over East China exhibits 40-50day oscillation feature in phase with the water vapor transportation from the South China Sea.