Abstract: The icing monitoring for transmission lines can effectively assess the icing condition and master the icing accident to reduce the damage caused by covered icing, which benefits the safe and stable operation of power system. Based on introducing traditional technology of icing online monitoring, the application of optical fiber sensing technology in transmission line icing monitoring was emphatically summarized. The principles, advantages and disadvantages of quasi-distributed fiber sensing（FBG）, distributed fiber sensing based on Raman scattering and distributed fiber sensing based on Brillouin scattering（Brillouin optical time domain analysis and Brillouin optical time domain reflectometer） were analyzed and compared in this paper. In addition, the distributed optical fiber sensing technology, which integrates sensing and information transmission, can master the icing condition of the whole transmission line without laying other sensors. Brillouin Optical Time Domain Analysis（BOTDA） of it has more obvious advantages in online monitoring of transmission lines since it can master for a longer distance and a wider range. The key issues based on distributed optical fiber sensing technology for icing monitoring were finally put forward and prospected at the end of this paper.