We study the occurrence of stochastic resonance phenomenon in the nonlinear bistable system when the forcing signal is at high frequency, based on the frequency shifting characteristic of Fourier transform. The simulation results show that after shifting the input frequency to a small one, and the output power spectrum peaks of the bistable system are strongly enhanced at this frequency by adjusting parameters. The ability of detecting weak signal overwhelmed in strong noise within a rather broad frequency range is improved in this paper.