The invention discloses a method for system for monitoring multi-dimensional deformations of electric transmission lines in real time on the basis of differential positioning. According to the methodand system, a base station is electrified to carry out measurement or increase measurement frequency, longitude and latitude information of the base station is updated in real time by utilizing a known base station coordinate, and a measured carrier phase observed value, a measured pseudo-range observed value and the base station coordinate are transmitted to a background server through a 4G network in an RTCM format or a self-defined format; a monitoring station uploads acquired field state data and a command for processing a client to the background through the 4G network in the RTCM formator the self-defined format; the background server receives the information sent by the base station and the monitoring station and carries out single-system and multi-system combined calculation; andthe background server converts the three-dimensional position of the base station into a longitude, a latitude and an altitude so as to obtain the position information, relative to the base station, of the monitoring station to complete the real-time monitoring. The method and system can be used for monitoring the multi-dimensional postures of electric transmission line towers on complicated geologies so as to ensure the safe operation of the electric transmission lines.