In the context of the NCAR daily reanalysis data of 1998,this paper investigates the source or sink features of atmospheric LFO (low frequency oscillation) over the Tibetan Plateau in summer 1998.Results indicate that sometimes the Plateau is a source region of LFO and sometimes is a sink area for the LFO of zonal wind. With further analysis of LF vorticity flux-divergence,it is found that at different time and place over the Tibetan Plateau LF vortex source (sink) has different distribution and propagation features.LF vortex source (sink) at 100hPa over the Plateau is influenced significantly by South Asia High.