This paper presents a scheme for analyzing the spectral structure of spherical functions of squared norm of anomaly field set using the coefficients of the function expansion,wherewith analysis is implemented of northern 500 hPa height for January and July in 1951～1986,separately. Results show that the spectral structure of the anomaly sets is characterized by low-dimension and low-order,and the salient features of the anomaly circulations and their seasonal/interannual variations can be accurately described in virtue of less than 50 components of the functions.