A detailed description of the stochastic resonance phenomenon is given, which is generated in process of determining the real modal of the system by modal stability diagram method based on auto-regressive and moving average(ARMA) time series model. The precise time-integration method is used to calculate the acceleration pulse response function on the finite element model of the cantilever, and then establish the ARMA model for vibration modal identification. It is found that the recognition results can be effectively improved by adding appropriate noise signal and the false modes can be eliminated in process of determining the real modal of the system by modal stability diagram method, namely the stochastic resonance phenomenon. After time-varying treatment of the cantilever beam, the stochastic resonance phenomenon is more significant compared with the time-invariant system and generate an obvious optimization to the final results.