The invention relates to an intelligent online monitoring and pre-warning system for cable operation condition. The intelligent online monitoring and pre-warning system comprises a monitoring terminal and a monitoring center master station, wherein the monitoring terminal acquires monitoring parameters of the cable operation condition, such as the grounding current of the metal protective layer of the cable, cable joint temperature, combustible gas content, poisonous gas content, oxygen gas content, smoke, water level and manhole cover security, in real time and reports the acquisition data to the monitoring center master station in a timing manner through a wireless network; the monitoring center master station is used for timely carrying out storage, statistic, analysis, display and processing on the reported acquisition data and has functions of acquiring synthetic data of cable operation, monitoring the operation state in real time, displaying image data, pre-warning a fault and giving an alarm, carrying out statistic analysis of information data and the like. The intelligent online monitoring and pre-warning system can provide an effective monitoring method for ensuring the cable trench line security, ensure that the high-voltage cable line runs stably and reliably and greatly improve the power supplying reliability.