The invention discloses a method for compensating electrode loss based on on-line discharge energy detection in an electricity discharge milling process, which is characterized in that the electrode loss is compensated based on the discharge energy amount between the on-line real-time detected electrode and a workpiece in the electric discharge milling process; the relation data of the electrode loss amount and the discharge energy is determined through a statistical manner according to the experimental measurement between the discharge energy and the electrode loss at the process condition that the process parameters in the process are the same; or the loss amount of the electrode relative to the discharge energy in the current phase is determined according to the discharge energy and the electrode actual loss at the previous phase of the electricity discharge milling process; the electrode actual loss is detected through the contact between the electrode and the datum plane which isarranged relative to the workpiece; and the amount of the discharge energy is sampled at regular time through the discharge power or current signals, and accumulated to obtain the discharge energy value. The method of the invention can preferably adapt to the changes of the workpiece shape and the processing state, and correspondingly dynamically adjusts the electrode compensation value, so as tolead the electrode loss compensation value to be more accurate in the electricity discharge milling process, thus improving the workpiece processing accuracy.