Abstract: The multicarrier underwater acoustic (UWA) communication faces the risk of modulation recognition and information security. This paper proposes a multicarrier spread spectrum UWA communication method based on orthogonal chaotic constellation modulation. By combining two channel M-ary spread spectrum modulation and multicarrier modulation, two-dimensional chaotic constellation symbols are designed to modulate the transmitted bits, which enhances the physical layer security. The receiver adopts an M-ary despreading method based on threshold denoising passive time reversal for large delay spread of deep sea UWA channel. Then, a passive time reversal improvement method is proposed based on the automatic multiscale based peak detection (AMPD) soft threshold denoising. The k-means clustering, statistical analysis and phase space reconstruction are used to analyze the communication security, and the bit error rate (BER) simulation on the deep sea UWA channel is performed. The simulation results show that on the premise of ensuring the reliability, the proposed method can effectively enhance the security of the multicarrier UWA communication system. In addition, the deep-sea experiment verification at the depth of the acoustic axis is tested. The proposed method achieves secure and reliable UWA communication with the communication distance of 150 km and the communication rate of 150 bit/s and the BER less than 1.16 × 10⁻⁴.