Abstract: The transmission line needs to be shut down during the traditional DC ice melting process, such process has limitations such as long ice melting time and harmonic pollution, In view of this situation, a method to achieve online ice melting of the transmission line based on the phase-shifting transformer is proposed in this paper. The theoretical calculation formula for deicing on-load transmission lines using phase-shifting transformer is deduced, and the calculation method of the active power, reactive power and voltage drop in the circulation ice-melting process is given. Secondly, based on the ice-melting current consumption requirements in the 220kV transmission line, the parameters of phase-shifting transformer for ice-melting are designed, and the equivalent circuit model of the phase-shifting transformer considering the changing impedance is established in MATLAB. Finally, considering the ice melting demand of the 220kV lines in the eastern part of Guizhou Power Grid Co Ltd, a simulation model is established. The voltage drop and reactive power compensation strategies of the lines during the ice melting process under no-load and load conditions are calculated. The research on deicing on-load transmission lines based on phase-shifting transformers provides theoretical support and engineering technology for deicing on-load transmission lines.