This present invention discloses an audio-separating apparatus and operation method thereof. The audio-separating apparatus applies both blind source separation and noise reduction mechanisms. The audio-separating apparatus only uses one microphone to record mixed sound signals. After applying the noise reduction mechanism, noise reduced signals and the mixed sound signals are used as the inputs of the blind source separation. The method may avoid the spatial aliasing effect caused by using a microphone array to record the mixed sound signals. Besides, speech segment losses caused by processing the noise reduction will be effectively recovered, which may help the hearing impaired recognize target speech signals.