The invention provides an interference signal recording device, a system and method for locating impairment sources in a cable network by means of the interference signal recording device: one interference signal recording device is installed on the headend of the cable network, another signal recording device is installed in a cable branch of the cable network via a signal coupler; both interference signal recording devices comprise samplers; each of the interference signal recording device starts to sample the interference signal at the moment when receiving a predetermined sampling timing signal from downstream signals; a computer is used for obtaining digital sample sequences of the interference signals obtained by sampling of the two interference signal recording devices via the Internet and for calculating a cross-correlation function of the two digital sample sequences; it can be determined whether an impairment source exists in a signal delivering path passing through the location of signal coupler in
