To realize the low probability of interception communication system, this paper presents a memory nonlinear model to carry on nonlinear transformation for channel transmission characteristic. When primary signals are transmitted through this kind of system, the quality of signals will be observably deteriorated due to strong memory effect nonlinear distortion. Located at the frequency range where primary signals are, the nonlinearities decrease primary signals' signal to interference ratio (SIR) and memory effect introduce inter-symbol interference (ISI). Hence, with the purpose of encryption, the proposed model is designed to change both amplitude-frequency and phase-frequency characteristics in channel. At receiving end, suffered from bad SIR and ISI, illegal user cannot obtain correct information by I/Q demodulation and sample sentence processing, while authorized users can easily recover the primary signals waveform by proposed inverse nonlinear transformation model and get correct information next. The experiment results are provided to verify encryption effect of our method and analyze the loss of signal to noise ratio (SNR) of authorized user is also discussed for evaluating the impact of encryption method on conventional communication process.