Abstract: Aiming at the parameter estimation of the actual subcarriers’ number in OFDM signals, the paper proposed an improved algorithm, which can improve the peak of detection, reduce the threshold of signal noise ratio and increase the precision of estimation by introducing stochastic resonance theory into the traditional method of cepstrum and wavelet transform. The simulation result shows that the improved algorithm based on stochastic resonance has strong robustness, it can greatly improve the local signal-to-noise ratio of the output from the system with reaching up to maximum of 14 dB. It can also effectively reduce the estimation error under extremely difficult condition of white gaussian noise channel with threshold lowering about 5 dB. This new method can lay a good foundation for the follow-up work of the received OFDM signals, such as information recovery and so on.