Abstract: Based on analisis of 100mb divergence,geopotential height and vertically -integrated moisture transport fields a discussion is concentrated on features of the upper circulation in the establishment of Asian monsoon in 1979 and in its medium - range oscillation.It is found that the establishment of the high-level divergence fields in different parts around the South-Asian High(SAH)leads to the set-up of summer monsoon in these regions, the fields at the central and eastern sections of the SAH ridge fine have a distnctive characteristics that feature the concurrent onset of Indian monsoon and the Chang-Jiang valley Meiyu and the antiphase of the monsoon to the rainy-season precipitation in South China.In eastern Asia, the easterly around the SAH is a good indicator of the northward march of summer monsoon while in India the Iranian High north-easterly (being a component of the SAH circulation) in the outer brim is indicative of the Indian monsoon onset.100 mb height fields in some domains and vertically integrated moisture transport fields in 40-50 day oscillation exhibit propagation eastward and westward over the Asian area" whereas the 20-30 day oscillation of the divergence field moves regularly toward the west after the onset of Indian monsoon.