Abstract: Climatological characteristics of water vapor budget over the southeast part of Tibetan Plateau and their impacts on ambient areas in summer are investigated based on NCEP/NCAR reanalysis data for the period from 1961 to 2005. The result shows that the southeast part of Tibetan Plateau is a moisture sink, under the seasonal average of summer condition, the water vapor net budget is 39.9×10⁶ kg/s. The establishment and advance of Asian summer monsoon play an important role in the incoming water vapor of the southeast part of Tibetan Plateau, and the outgoing moisture is closely associated with the advance and retreat of rain belt of East China. The southeast part of Tibetan Plateau, as the moisture transport channel to the east of Northwest China and mid-lower reaches of the Yangtze River, plays a great role in the moisture budget around it. The southeast part of Tibetan Plateau, as a transferring station, is one of the key factors to the flooding anom alies of precipitation in mid-lower reaches of the Yangtze River and the drought anomalies in North China. By power spectrum analysis, it is found that there is quasi-biennial oscillation in the interannual variations of moisture budgets at east/north boundary over the southeast part of Tibetan Plateau and summer precipitation of mid-lower reaches of the Yang tze River/eastern part of Northwest China. An in-phase inter-annual variation are shown by the moisture budgets at east boundary over the southeast part of Tibetan Plateau and the summer precipitation of mid-lower reaches of the Yangtze River, and the same to moisture budgets at north boundary and the summer precipitation of eastern part of Northwest China.It shows that the quasi-biennial oscillation of moisture budgets at east boundary is closely association with that of precipitation in mid-lower reaches of the Yangtze River, and the quasi-biennial oscillation of moisture budgets at north boundary is closely association with that of precipitation of the eastern part of Northwest China.