Abstract: For the difficulty of separation of accompaniment from mono music, a kind of music accompaniment separation method based on two-dimensional Fourier transform (2DFT) was proposed, first of all, mono music was transformed by two-dimensional Fourier transform into a two-dimensional sonogram. Secondly, the position of periodic peak energy was determined by image filtering, and then masking matrix was constructed by rectangular window to extract the constituent of the music accompaniment. Finally, the accompaniment of the time-domain signal was restored by means of inverse transformation. The simulation experiments show that the method in this paper has an advantage over other separation algorithm. The separation index SIR can be improved by about 0.5-4 dB, and SAR by more than 15dB.