The present invention relates to a non-invasive power load decomposition method, and belongs to the field of power measurement technologies. The method comprises: first collecting instantaneous current when each power device is switched, and introducing a primary function to decompose the instantaneous current, so as to obtain a current amplitude when each power device is switched; using a minimum value of a difference between a current amplitude at a user power inlet and a current amplitude of each input power device as an objective function; and solving the objective function by using an optimization algorithm, wherein an obtained result is a switching situation of each power device in power load. According to the method provided by the present invention, the switching situation of power load can be acquired online in real time, the decomposition method has relatively high precision and relatively good stability, and a computation speed is high. The present invention can be applied to a plurality of technical fields such as power system load monitoring, power analysis, load energy saving, load prediction and load modeling, and has a significant meaning to energy saving of the whole society and power system planning and operation.