An online monitoring method for dynamic changes in positions of transmission line conductors based on electromagnetic signals of ground wires and an apparatus are provided. The method includes: monitoring electromagnetic signals of ground wires; in response to changing in the electromagnetic signals, sending waveforms of the electromagnetic signals of the ground wires before and after changing to a data processing end; deducing change situations of mutual inductances between the ground wires and conductors based on values of conductor currents and the change situations of the electromagnetic signals of the ground wires, and further deducing position change situations of the conductors based on the change situations of the mutual inductances between the ground wires and the conductors; and obtaining dynamic changes in positions and movement statuses of the transmission line conductor based on the position change situations of the conductors.