A karkashin al’ada yanayi, da aiki system of electrical equipment, generally divided into continuous operation, short-term operation, continuous short-term operation system, The principle of Load lissafi is to replace the rated power of electrical equipment under different aiki systems with the same long-term working system. The lissafi of distribution transformer load is a complicated process, therefore, it needs a lot of calculation and repeated verification by professional staff, in order to get the correct calculation results.