Abstract: The initiation and distinctive establishment of the East Asian subtropical rainy season and its nature of precipitation are discussed based on the 1961-2006 NCEP/NCAR reanalysis data, the TRMM rain data and the CMAP rain data. The results show that at the end of March a wide range of strong precipitation begins to appear in the subtropical areas in eastern China with the daily precipitation more than 6 mm with the water vapor in the lower levels (from ground to 700 hPa) coming mainly from the southwest moisture transport turned in the south of the western Pacific subtropical high suggesting that the subtropical monsoon rain season is beginning. Meanwhile the seasonal reversal of the zonal pressure gradient (the landsea thermal contrast) between East Asia and the middleeastern Pacific takes place. The subtropical regions in East China begin to hold a heating centre accompanied by ascending motion. Several pentads later the intensity of the heating and the convective height which are gradually increasing are equivalent to those in the tropics. The convective instability atmosphere in the middlelow levels is of. At the same time the South China Seathe western Pacific region is still under the control of the subtropical high with sinking motion prevailing without precipitation, and the South China Sea Summer Monsoon (SCSM) and its related water vapor passage have not been established yet. The establishment of the East Asian subtropical monsoon rainbelt is earlier than that of the tropical monsoon rainbelt. In addition, the two rain bands show the respective independent heating centers as well as the associated ascending motion. At the time of the onset of the SCSM, the heating center over the South China Sea rapidly moves northward to the subtropical area.