The invention discloses a current differential protection method suitable for a variable frequency motor. Through HHT (Hilbert-Huang Transform), the amplitude and phase information of each frequency component of non-stable signals is acquired, the frequency component with the maximum energy (maximum amplitude) is selected as a main frequency of the signals, the actual running condition of the variable frequency motor is considered, the main frequency component is the main component of the signals and other frequency components can be regarded as harmonic components. The main frequency components subjected to HHT of three-phase current at the head and tail ends of the variable frequency motor are taken to calculate phasor differential to form the HHT-based differential protection principle. The current differential protection method can automatically adapt to the running conditions of the variable frequency motor under different frequencies, and avoids the problem that the traditional power frequency differential protection method cannot protect the variable frequency motor.