Abstract: The onset and advance of the summer monsoon in the East Asia were inverstigeted using the outgoing longwave radiation (OLR) data and conventional meteorological data. The advance of the summer monsoon displays pronounced nonuniformity on the time and space. The westerly disturbance moved from the Southern Hemisphere has marked influence on the wind transform from easterly to westerly over the southern and centre regions of thd South China Sea. It has relation to the equatorial eddy located at 105°E. Maybe this eddyis.an onset vortex of the summer monsoon over eastern Asia similar to the situation of the Indina monsoon.