Abstract: The large-scale circulation of Mei-yu system over East Asia has been reviewed from dynamical climatalogical view in.this paper, Following arguments have been pointed: Mei-yu phenomenon is occurrence in the transition region between the Indian Summer Monsoon System and the trade wind (or Hadley) system over the tropical North Pacific; Mei-yu front belongs to a semi-tropical and semi-extratropical weather system; the heavy rain occurred at Mei-yu front is caused by the disturbances of subsynoptic systems to the front. The conceptional models for the large-scale circulation and various subsynoptic disturbances of Mei-yu system have been given.