Blind demodulation is one of the most important technologies to obtain useful information on non cooperative digital communication signals. This article firstly summarizes the blind demodulation of existing digital communication signal. And then it further improves the theory and noise reduction algorithm of nonlinear dynamical system on the basis of our published paper to blind demodulation the random bit stream on carrier frequency modulated by BPSK with negative SNR. The test results show that Bit error rate is 0, using nonlinear dynamical system noise reduction under Eb/N0>7dB and blind demodulation error curve of noise reduction is lower than the error curve of existing non coherent demodulation method under 0 < Eb/N0 < 7dB. Therefore, the blind demodulation of nonlinear dynamical system noise reduction compared with existing non coherent demodulation at least improves the processing capacity of 7 db. Test results show that the research results provide an effective method of blind demodulation for electronic reconnaissance signal processing.