There are many reports on extracting the single frequency signal under noise by the stochastic resonance, but in which the information that the signal carries is zero. The experimental investigation in this paper manifests, when it is driven by an amplitude modulation wave and white noise, not only that the output of nonlinear bistable system exhibits the stochastic resonance phenomenon, but also that the modulation signal (information signal) can be extracted from the output by detecting and filtering. As compared with that from the electronics system by detecting and filtering direct the signal-to-noise(SNR) of modulation signal f rom the nonlinear bistable system is higher. Under the condition of adiabatic ap proximation the analytical formulation of the SNR of modulation signal is provid ed.