In order to analyze the modulation characteristics of vibration response signals caused by different rotorstator rubimpact faults, based on the Jeffcott rotor model, this paper utilized the variational mode decomposition and Hilbert transform to extract and analyze the intrawave modulation characteristics of different rub impact fault simulation signals, and reveals the relationship between the dynamic characteristics of rubimpact rotor and the intrawave modulation characteristics of fault signals. The simulation results show that the periodk rubimpact fault can cause the vibration response signal in the medium and low frequency band to oscillate its instantaneous frequency at the center of 1/k octave, and the vibration frequency is still 1/k octave, which results in the 1/k side frequency band in the original frequency spectrum. In the quasiperiod rubimpact fault, the internal frequency modulation is irrational octave and integer octave close to 1/k octave, which results in the irrational number side band in the original signal spectrum. The rotor fault diagnosis test of centrifugal pump showed that the intrawave modulation characteristics can effectively be used to identify the severity degree of rotor rubimpact fault.