Abstract: Based on 13 year monthly mean wind and 2 year day -to-day wind for Northern summer (May to September), a study on the climatological features and medium -range oscillations of South Asia tropical easterlies at 200 hpa was made. The significant intraseasonal and interannual changes in the TEJ characterized by 5 kinds of anomalous patterns, and its close relationship to low latitude upper -tropospheric, broad -scale circulation anomaly and to South Asia summer monsoon, were discussed .Three kinds of medium-range oscillation in the easterlies were found. The quasi -50 day oscillation related to the summer upper-tropospheric, broad-scale divergent changes over South A-sia possesses southward phase propagation over summer monsoon region. It was also found that the quasi - 50 and 25 day oscillations assume prominant interannual change. In the year with weak quasi -50 day oscillation, the dominant oscillation of low latitute planetary wave, which shows equatorward phase propagation and systematic westward propagation, is the quasi - 25 day oscillation. The biweekly oscillation, in general, propagates westward in the easterlies.