Abstract: In recent years, extreme low temperature weather poses a great threat to the reliability of power grid. DC ice melting technology is an effective technical means to deal with low temperature ice and snow weather. However, the DC ice melting device installed in the power grid system contains a large number of traditional semi controlled power electronic components. A large number of harmonic currents and certain DC components will be generated on the AC and DC sides. After invading the AC side, the DC bias phenomenon of the transformer will occur, resulting in the heating and temperature rise of the transformer core, and serious damage. This paper studies the DC ice melting device of Guishan substation and its harmonic and DC component characteristics, further studies the influence of harmonic and DC component produced by DC ice melting device on dry-type transformer in the system, and gives the theoretical derivation and analysis of this process, which provides a theoretical basis for further guiding the operation of DC ice melting device and eliminating the influence of harmonic and DC component on dry-type transformer。