The utility model relates to a cross-frequency-band power-line carrier communication system. The system comprises a power line carrier machine which is connected with a power line. The power line carrier machine comprises an analog front end for performing amplifying and outputting a transmitting signal and performing filtering, adjusting and automatic gain controlling on a receiving signal. The analog front end comprises a microcontroller MCU and a carrier channel which are successively connected. The system can realize full duplex communication and full-frequency-band power-line carrier communication with frequency band in a range of 30Khz-20MHZ. According to the cross-frequency-band power-line carrier communication system, the available spectrum bandwidth is expanded to 30kHz-20MHz, and therefore the available bandwidth is much wider than the bandwidth of the analog front end of the existing carrier machine, thereby enlarging channel bandwidth of the power line carrier communication, and improving spectrum utilization rate, narrow band carrier communication rate and narrow band carrier communication distance in the power-line carrier communication system.