The spectrum of stator current in the rotor slot harmonics of induction motor are extracted by adopting FFT method. It has disadvantages, such as low frequency resolution, poor denoising, frequency spectrum leakage. It is difficult to improve the measurement sensitivity and antinoise. A new method was presented, in which the rotor slot harmonic frequency was extracted from the current spectrum of the motor stator by using HOC-MUSIC to accurately estimate the motor speed. The MUSIC method has high frequency resolution and a kind of ability for strong weak harmonic detection. At the same time HOC can effectively suppress noise. HOC-MUSIC was applied to extract the rotor slot harmonics to estimate the motor speed in serious noise case. The experimental results show that this method is feasibility and effectiveness for estimating the motor speed by extracting the frequency of the rotor slot harmonic. Compared with traditional FFT method, this method has good estimation precision and dynamic characteristic.