Results of the Maximum Entropy Spectrum analysis and thefiltering analysis are given by using the ECMWF analysis data of the 500 hPa geopotential height over the Qinghai-Xizang Plateau and its surrounding areas during the summer half year.It is shown that the 30-60 day oscillations are significant over the Plateau and its vicinity.The center of the 30-60 oscillations is found in the eastern part of the Plateau. The annual variations are also discussed.