The present invention relating to a technical field of network communication discloses a method of processing signal crosstalk, a device thereof and a frequency spectrum management system. The method comprises the steps of combining multiple frequency points on a digital user line frequency band to obtain a frequency point group; calculating by using a sending power spectrum and a receiving noise spectrum power spectrum of the digital user line in the frequency point group to obtain a crosstalk amplitude value of the digital user line in the frequency point group. According to the present invention, crosstalk amplitude value in a DSL line can be obtained without changing the current device or adding additional devices.