The stator current was first demodulated by the TeagerKaiser energy operator, thus this could effectively eliminate the effect of the supply component spectral leakage on extracting the speed harmonic component. Then the influence of SDTFT on the precision of speed estimation was analyzed, and a new method for mSDTFT frequency analysis used to speed estimation was proposed. The mSDTFT method largely reduced the computational overhead, especially for certain spectrum lines that need. The mSDTFT method also could improve the flexibility and effectiveness of spectral analysis. Experimental results showed that the proposed method could validity extract the speed harmonic component under different load conditions, and had high precision of speed estimation.