Aiming at the difficulty of the incipient stage of rotor bar broken fault, a fault monitoring method based on reconstruction of variational mode decomposition(RVMD) is proposed. This method aims at the variation problems of detection signal structures and solves many mode functions, so as to realize the fault detection in virtue of the superposition of reconstruction. Then, combining with the concept of the damage factor, this paper proceeds to model the rotor bar broken fault in the incipient stage. With the use of the built fault model, this paper realizes the rotor bar broken fault injection in the incipient stage and carries on the fault monitoring experiement. The experiment verifies the validity of the proposed methods.