The invention relates to a load reduction quantity calculation method based on subentry measure, and the technical characteristics of the method lie in that the method comprises the steps: 1, setting minimum power values after the timing of a demand response event is started; 2, respectively collecting the real-time power values of switching type branch circuits, quick adjustment type branch circuits and slow response type branch circuits, respectively comparing the real-time power values with the corresponding minimum power values set after responding: replacing the minimum power values set after responding with the collected real-time power values if the collected real-time power values are less than the minimum power values set after responding; 3, continuously collecting the real-time power values of all branch circuits in a circulating manner, and carrying out the comparison and replacement of the collected real-time power values of all branch circuits with the current minimum power values of the corresponding branch circuits till the demand response event is finished; 4, solving the actual load adjustment values of all branch circuits. The method can complement a conventional load prediction mode, and carries out the mutual verification of the load reduction quantity, so as to reduce the authentication divergence of the load reduction quantity.