The invention discloses an aluminum electrolysis cell molten aluminum interface fluctuation and pole distance online monitoring method and device. A clamp of an anode rod (1) and a carrier device (2) are connected through a carrier signal line, a binding post preinstalled in a cathode steel bar explosion welding block (5) and a signal receiving device (3) are connected through the other signal line; the O end of the carrier device (2) and the N end of the signal receiving device (3) are connected to form a measurement loop; the carrier device (2) loads a sinusoidal signal of the specific frequency f towards the measurement loop and the pole distance is measured; the signal receiving device (3) and an industrial personal computer (4) are connected; the signal receiving device (3) receives input voltage UAO and output voltage UMN data and transmits the processed data to the industrial personal computer (4); therefore, an electrolysis cell is equivalent to an inductance, capacitance and resistance (LCR) circuit, and the pole distance can be worked out by calculating the amplitude ratio between the output voltage UMN and the input voltage UAO.