The invention discloses a real-time and stage theory line loss fast estimation method with the clustering technique adopted. The method comprises the steps of extracting a real-time fracture surface feature vector, calculating a center fracture surface weight coefficient vector matched with the real-time fracture surface feature vector, fracture surface clustering, and theory line loss calculation. According to the real-time and stage theory line loss fast estimation method with the clustering technique adopted, when data are collected completely, center fracture surfaces are extracted by means of the nearest-neighbor clustering technique, and then fracture surfaces with similar operating states in a power grid are gathered together; under the situation of data missing, a central moment close to the data missing moment is found out by means of the nearest-neighbor clustering technique, and transmission loss of the power grid at the moment is assigned to the data missing moment; therefore, stage and real-time theory line loss values can be obtained fast, stage theory line loss calculation is achieved, the speed of the stage theory line loss calculation is increased, and precise comparison between the statistics line loss rate and the stage and real-time theory line loss values is achieved.