Abstract: with the continuous improvement of mechanization operation in Chinese coal mines, coupled with the huge demand for coal, the power of mining equipment in coal mines continues to increase, and the use of non-linear loads such as frequency converters is also increasing, as a result, the harmonic content in the underground power supply network of coal mine increases rapidly, and the influence of the harmonic on the mine flameproof mobile substation becomes more and more obvious.In order to improve the safety, economy and reliability of power supply for underground equipment in coal mine, the causes of harmonic wave in underground power supply system and its harm to mine flameproof mobile substation are analyzed.From the aspects of mining flameproof mobile substation involved, underground power supply system's variable capacity and connection group selection and the application of harmonic suppression technology of mine frequency converter, a method to reduce the influence of underground harmonics on mine flameproof mobile substation is proposed.