The high-resolution frequency-wavenumber method is a frequently used method to obtain the dispersion information of the dominant surface waves from the perspective of energy by calculating the F-K spectra. However,since the energy of the higher-mode Rayleigh waves is usually lower than that of the fundamental mode,it is often difficult to separate the multi-mode dispersion information. In this paper,an improved high-resolution frequency-wavenumber method for mode separation which establishes a multi-mode Rayleigh waves model is proposed,and its characteristics of phase velocity,wavenumber and energy is discussed. By enhancing the higher-mode energy on the F-K spectra,extracting its local extremums of multi-mode energy to get the phase velocity points,and fitting the probability distribution of all phase velocity points,the multi-mode dispersion curves are extracted. The engineering application shows that the improved method can better restore the information of multi-mode Rayleigh waves,and through the joint inversion of the extracted multi-mode dispersion curves,it is capable to match the shear wave velocity structure with the engineering borehole results.