Frequent icing disasters on transmission lines have brought a great threat to the power grids. Most existing studies ignored the effects of time-varying meteorological conditions. To effectively predict the growth in line icing and provide reference for transmission line deicing and early warning of galloping, on the basis of the icing mechanism of conductors and the Euler gas-liquid two-phase flow model, we proposed a numerical simulation method for icing of transmission lines under the influence of time-varying meteorological parameters. A numerical simulation framework of conductor icing growth was established based on FLUENT and FENSAP-ICE software. The influence of different parameters on the quality and shape of the ice coating on the conductor of the transmission line was analyzed using 3D simulation model. Results show that the ice coating shape of the conductor was greatly affected by the wind speed, the median volume diameter of the supercooled water droplet, the liquid water content in the air, and the diameter of the conductor, but little affected by temperature. Finally, the validity of the simulation calculation method was verified by using the on-site icing monitoring data of real transmission lines and the corresponding meteorological data. The prediction results were in good agreement with the monitored results of transmission line icing, indicating that the proposed method has good accuracy.