<b>A Method to Calculate Functions of the Product of G and F Used in Wilson’s GF Matrix Method</b> Wilson’s GF matrix method is generally utilized to obtain normal vibrations and normal coordinates of molecules. The function of the product of G and F in Wilson’s GF matrix method is also a key to determine the line shape function LSF which expresses molecular absorption or emission spectra. In this paper, the method for calculating the function of the product of G and F is shown. Line shape function, GF matrix method, a method to calculate functions of matrix 2516-2519 Issue-4 Volume-2 Hiroto Kikuchi