Abstract: A low probability of intercept (LPI) signal for underwater acoustic remote control，which is obtained by utilizing time-frequency spreading technique, is proposed in this paper. Both the Multi-carrier technique for time spreading modulation and the direct sequence spreading spectrum technique (DSSS) are used in the signal design. The relationship between Time-Band width and LPI performance is analyzed, and the comparisons of the energy distribution between original signal and modulated signal are also made. The concept of detectable distance is applied to quantifying the LPI performance. Theoretical analysis and computer simulation indicate that this LPI signal has advantages in lower instantaneous power and spectral density, higher processing gain, and closer detectable distance, and so it can be used reliably to achieve the information transmission with a low probability of intercept.