Abstract: Through testing and analyzing electromagnetic environment of central substation of coal mine underground, following conclusions were gotten: 1 There is low-frequency interference nearby high-voltage switch during normal operation of equipments in central substation. 2 When transformers of center substation run normally, the EMI is mainly below 500 MHz and a greater interference appears nearby 100 MHz, and the maximum interference is 40 dB?μV/m higher than background noise or so. 3 When the switch in central substation is taken on or off instantly, there will be a greater EMI which is mainly below 1.5 GHz. The larger interference is in low-frequency and the maximum EMI reaches 193 dB?μV/m. 4 When equipments of central substation are in normal working, radiation of electromagnetic field reaches 1 standard level 1 V/m. But when the switch is taken on or off instantly, the EMI is larger than 2 stardard level of GB9175-88 environmental health standards of electromagnetic waves because the EMI is larger below 1 MHz.