This system adopted two-level structure that was composed of Cable Monitoring And Controlling Device (CMCD) and Cable Monitoring Center (CMC). CMC receives the alarm data via the MODEM and the telephone net. In this way, the functions of typing the fault point's map, alarming and the cable management can be picked up. CMCD takes the processor chip Atemega128 as the center of the system that adopted the alternating current and direct current on-line switching electricity-supply mode. Also, the system includes four groups of independent power, the relay and the optical isolation to separate the system from the monitoring cable and the telephone net. CMCD accomplishes the cable real-time monitoring, malfunctions auto-locating, telephone voice alarming, long-distance parameters modification, data up-loading, error verifying and the telecommunication room's environment monitoring and so on. The longest distance of monitoring cable is 20 km, and the precision is 1%.