An underwater acoustic communication system of 1.064 μm pulse laser is established. According to the mechanism of laser acoustic,the relationship between the laser pulse energy and the acoustic energy is studied,and the characteristics of laser acoustic signal and transmission under water are analyzed. Aiming at the spectrum characteristics of noise signal and laser acoustic signal,filtering method is used for effective signal separation in frequency domain. Theoretical analysis and experimental results show that acoustic energy increases with the increase of laser pulse energy,and different optical structures can obtain different acoustic energy. Frequency adjustable ASK code modulation can realize the effective transmission of digital information,which provides a new technical method for marine communications.