The invention discloses a hard disk camera system which comprises a hard disk video cassette recorder, a video display device and at least one video camera, wherein the hard disk video cassette recorder is connected with the video display device through signals, and a first twisted-pair interface, a differential demodulation module and a signal output module are connected in the hard disk video cassette recorder in sequence; the first twisted-pair interface is connected with the video camera through a twisted pair so as to receive a video signal differentially processed by the video camera; the differential demodulation module is used for demodulating the differentially processed video signal; and the signal output module is used for transmitting the demodulated video signal to the video display device. The hard disk camera system of the invention can increase transmission distance and enlarge the application range of the hard disk camera system by using the twisted pair to transmit the video signal between the video camera and the hard disk video cassette recorder, can reduce material cost, and can increase transmission stability because the intermediate conversion links of a signal transmission path are reduced. The hard disk camera system can ensure transmission quality, avoid or reduce the phenomena of video distortion, video delay and the like.