The invention relates to a method for purifying an axis track under a variable rotating speed working condition. The method comprises the following steps: calculating time-frequency spectrums of vibration signals in X and Y directions; extracting an instantaneous frequency sequence of main frequency components of the vibration signal in the time-frequency spectrum one by one, and carrying out datafitting on the instantaneous frequency sequence; subtracting the instantaneous frequency value at the initial moment from the fitting result of the instantaneous frequency of each extracted main frequency component, and integrating the obtained result to obtain a phase sequence; generalized demodulation is conducted on original vibration signals in the X direction and the Y direction through theinstantaneous phase sequence, and the frequency changing along with time under the variable rotating speed working condition is converted into the frequency not changing along with time; extracting main frequency components in the demodulated signal one by one by adopting a phase difference frequency spectrum correction method, and adding the main frequency components to reconstruct the signal; and synthesizing and purifying the axis track by using the vibration signals reconstructed in the X direction and the Y direction. The method is not interfered by random noise, the influence of vibration amplitude change on the shape of the axis track under the variable rotating speed working condition can be avoided, and discrimination of the shape of the axis track is facilitated.