Abstract: Aiming at the problems such as short service life, low monitoring precision and slow transmission speed, the traditional tension tilt sensor and camera monitoring system are used to monitor the icing thickness of HV transmission line for a long time. In this paper, a real-time monitoring system of transmission line icing based on beidou Navigation and communication technology is designed. The system uses the principle of the Beidou carrier differential positioning to accurately obtain the high precision 3 D position coordinate information of the transmission line, and then unifies the position coordinate information under the Cartesian coordinate system to correct the position error, according to the variation of transmission line position, the length of transmission line and the installation position of instruments in time domain, the calculation model of icing thickness is built, and the model is embedded in the terminal of intelligent conductor location, and the monitoring network of transmission line is constructed, to realize the monitoring of transmission line icing thickness in full time and in full position. Through indoor and outdoor experiments, it is proved that this system can realize real-time monitoring and feedback of transmission line icing with millimeter-level precision and millisecond-level speed.