Icing identification technology of optical fiber composite overhead ground wire (OPGW) is studied based on fiber Brillouin scattering. Thermodynamic theoretical derivation of identification technology is given, and then temperature distribution of conductor is simulated with the finite element method by Comsol Multiphysics. And the results show that icing area is dull to the change of ambient temperature. Hence ice-coating on transmission lines can be identified through temperature variation in a period of time. Based on the results, OPGW icing identification system based on fiber Brillouin scattering is designed using Brillouin Optical Time Domain Reflectometer, which solves problems of insufficient power and electromagnetic interference in traditional identification systems. This system is successfully applied to the Zhaotong power system with detection range 75 km and temperature error ±2 ℃.