The invention relates to a method for real-time determination of disturbance of an identification signal of low-frequency oscillation of a power system. The method comprises the following steps that: real-time acquisition of N identification signal data of low-frequency oscillation of a power system is carried out, wherein the data are changed with time and are taken as basic data; after the data are processed by erosion transformation, expansion transformation, and gradient transformation, a soft threshold are calculated and then a determination sequence value is obtained; determination for a disturbance state of an identification signal of low-frequency oscillation is carried out; and the basic data are updated and the previous steps are executed again. Therefore, an objective of real-time determination of disturbance of an identification signal of low-frequency oscillation of a power system can be allowed with cyclic repetition of the all steps. According to the invention, whether a present identification signal of low-frequency oscillation is in a stable state or in a disturbed state can be real-time determined accurately, and then an early warning system of low-frequency oscillation of a power system can employ a corresponding technical treatment method according to the determined state; consequently, effective and reliable identification of a low-frequency oscillation mode of the power system can be allowed, thereby laying a solid foundation for accurate early warning and damping control of the low-frequency oscillation.