The invention discloses a method for positioning an oscillation disturbance source in a power system. The method comprises the following steps of: acquiring voltage, current, power physical quantity of a plurality of measuring points in a multi-voltage class power grid and meeting the following conditions: 1, whether each measuring point is subjected to low-frequency synchronous power oscillationis monitored in real time, and an oscillation amplitude, a main oscillation mode frequency, main oscillation mode damping, an initial phase of the main oscillation mode and oscillation initial time information are provided; 2, two frequencies in the main oscillation mode of the measuring points which are subjected to low-frequency oscillation accord with the condition that an absolute value of delta f is less than delta Fset; 3, the oscillation initial time of the measuring points which are subjected to low-frequency oscillation has a sequence relationship, and a clear characteristic that theoscillation starting time of measuring points in a low-voltage class power grid is earlier than the oscillation starting time of measuring points in a high-voltage class power grid; and 4, the average frequency fave of the main oscillation mode of each measuring point which is subjected to low-frequency oscillation accords with the condition that fave is more than fmin and less than fmax; and when the conditions are accorded, determining that the power system is subjected to low-frequency oscillation and a local power grid in an area with the earliest oscillation starting time is the oscillation disturbance source.