Abstract: Some diagnostic methods of CEOF, power spectrum and bandpass filter wave were applied in this paper to analyse the seasonal northward beating of the subtropic high with the daily date of the 500hPa geopotential height field divided by the grid spacing of 2.5°x 2.5°. It was concluded that it is a global phenomenon that the subtropical high seasonally beats northward and this beating propagates westward; the origin of the beating caused by the disturbance field mainly lies in the Arabian Sea and the middle Pacific Ocean area and the sink area is the east Pacific Ocean; During the seasonal beating of the subtropic high and the westward propagation of this beating low-frequency oscilliation act as a very important role. The difference of the subtropic high's beating per year depends on the change of disturbance origin and the low-frequency wave it excites.