Abstract: An empirical orthogonal function analysis is performed by using the observed 500hPa monthly mean geopotential height field in the northern winter for 34 years, and then a statistical analysis is made for the relationship between the first five principal components and the barotropic energy conversion process. The results show that it is helpful to the generation and maintenance of low-frequency circulation anomalies throughout the barotropic energy transfer from basic flow-frequency disturbances.