We demonstrate the possibility of determination of the structural constant S and the average size of crystallites in an anisotropic nanocrystalline magnetic film by the analysis of the shape of the sharp microwave absorption peak observed when the external magnetic field is swept along the hard magnetization axis. In the theory of magnetization ripple, the constant S is linked to the surface density of local magnetic anisotropy energy and S can be used to estimate the quality of nanocrystalline films. The performance of the new method for determination of S was demonstrated on a 300-nm-thick nanocrystalline Co-P film. The absorption spectrum was measured on a local film area of ~ 1 mm2 by the scanning ferromagnetic resonance spectrometer. The calculated from the analysis of the spectrum value for S allowed us to determine an average size of crystallites in the film that agrees well with the transmission electron microscopy results.