This paper design a detection program for multifrequency weak signal based on the method of bistable stochastic resonance with the thought of separation of frequency band in spectrum monitoring. Normalized scale transformation is used to complete the simulation of stochastic resonance detection of periodic signals in high frequency range. Aiming at the limitation of the stochastic resonance method for the multifrequency signal detection, the wavelet transform and the normalized stochastic resonance are conbined to achieve the multifrequency weak signal detection simulation experiment with the characteristic of wavelet transform that can separate the frequency band. The simulation results show that the normalized stochastic resonance scheme combined with the wavelet transform can detect the multifrequency weak periodic signal in the frequency band to be measured.