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Due to the rapid development of modern communication technology and the substantial improvement of the processing capacity of communication equipment, it has become a challenging and meaningful research direction to realize the covert transmission of information by ensuring the low probability of detection (LPD) performance of the communication signals. The disadvantage of traditional fixed-parameter signal in LPD gradually appears. The paper proposes a time-varying chaotic multitone communication method to accomplish the LPD for the eavesdroppers. The method gets rid of the conventional LPD communication method whose performance improvement is exchanged at the expense of its reliability loss or sacrificing more resources. Based on the original chaotic multitone (CMT) communication method, the time-varying parameter is introduced to improve the randomness of the waveform and thus reduce the detection probability of eavesdroppers to the single tones in the multitone group (MTG). Meanwhile, to improve spectrum efficiency and reduce system complexity, the corresponding communication system model is designed based on orthogonal frequency division multiplexing (OFDM) technology. After given the corresponding detection and demodulation scheme based on the diversity and combination, the influence of time-varying parameters on the reliability for the cooperative receiver is analyzed. The LPD contribution of this method is evaluated by analyzing the detection probability of the eavesdropper. The experimental results show that the proposed method not only maintains the original reliability but also reduces the detection probability of eavesdroppers under the constant false alarm probability detection scheme.