The present invention provides an area measurement decoupling-based low-voltage distribution network loss calculation method. The area measurement decoupling-based low-voltage distribution network loss calculation method is characterized in that according to an area decoupling viewpoint, and by combining the distribution condition of the measurement devices, a low-voltage distribution network that is complicated in structure and abundant in branches is decomposed into a plurality of small areas, and each small area is used as a loss calculation unit; in each decomposed small area, by utilizing the data information of the head and tail measurement nodes and the coupling relation between the areas, and by adopting a forward-backward sweep method and a least square method, the node loads and the voltages in the areas are estimated to obtain the estimated values of the area loss, and the total loss of the distribution network is obtained by adding all area loss. A loss estimation method adopted by the present invention is small in needed information amount, is simple and convenient to program and calculate and is especially suitable for the low-voltage distribution network loss estimation that is incomplete in measurement devices and limited in data obtaining, and finally, the validity of the loss estimation method provided by the present invention is verified via examples.