The invention discloses an intelligent on-line monitoring system for cable line faults. The intelligent on-line monitoring system comprises a plurality of fault detectors, a centralized processor, a communication exchanger and a monitoring system server. A 2.4 G wireless communication module, a single chip microcomputer control unit and a current sensor are arranged in each fault detector. The centralized processor is connected with the monitoring system server through the communication exchanger, receives the sampling data of an ABC3 phase fault detector to conduct initial fault information calculation, and transmits the processed and analyzed data to the communication exchanger. The communication exchanger decodes the fault information and then uploads the fault information to the monitoring system server. The intelligent on-line monitoring system for cable line faults can comprehensively monitor the fault conditions such as short circuit, grounding, overload, line breaking, power failure, three-phase imbanlance and burglary and cutting on a line, and fault judgments are quickly and accurately made.