Abstract: Discusses the noise and its frequency band produced both by a 5t magnetic mirror bi-electic DC EAF and the same size three-phase AC EAF during melting period in the steelmaking workshop of Beijing Heavy Machine Plant, as well as the stable-constant magnetic field produced by a magnetic mirror coil. Compared with the three phase AC EAF, the DC EAF is an idel steel-melting equipment of steelmaking. The noise, which is mainly composed of high frequency,has been decreased by 15dB during melting period. Has used a DC EAF, artificial stiring is not necessary in whole operation because of its high stiring strength in melting pool. The arc is stable and has a certain direction in burning so the temperature in melting pool can be increased with a high speed (4-6)℃/min.