Abstract: A new speech enhancement approach based on H_∞ filtering and adaptive conjugate gradient parameter estimation is proposed.In this approach no a priori information of noise statistics is required when conducting adaptive speech parameter estimation from noised speech.One assumption needed on the noise is that noise signal has finite energy.On the basis of H_∞ filter，minimization of the performance index deterioration of this algorithm caused by additive noise is guaranteed.Simulation results show that this speech enhancement algorithm is fast，robust，effective，easy to implement with single speech input channel，and can restrain complicated background noise.