Mother wavelet function “db12” was adopted for rotor fault with different rub-impact degrees. The displacement signals were decomposed into 6 levels. Reassigned Morlet wavelet scalogram has been used to extract fault features for wavelet frequency bands with obvious time-frequency features. The decomposed signals in different decomposed levels together with their frequency-band energy ratios were discussed in details. The results showed that fault features could be extracted well by combining two mother wavelet functions and frequency-band energy plot in different rub-impact conditions. In the stage of slight rub-impact, high and low frequency components are all small; in the stage of moderate rub-impact, stable X/2 based harmonic components occurred and in the stage of serious rub-impact , the energy of harmonic components are greater than rotational frequency and reached the maximum. 