A new speech enhancement scheme based on higher order cumulants (HOC) is proposed. Under the condition of Gaussian noise, a method for estimating the probability of speech absence in each frequency bin of each frame is devised based on HOC. Further, a kind of modified Minimum Mean Square Error (MMSE) estimator based on HOC is proposed. Objective measurements and subjective tests show that the proposed algorithm could restrain the residual noise and "musical noise" more effectively than the traditional spectral subtraction method and MMSE method particularly under the condition of low signal-to-noise ratio (SNR).