Abstract: An underwater acoustic communication scheme is described.It uses time delay among CW narrow pulses filled with different frequencies and frame synchronous CW narrow pulse to carry information.The receiver uses time delay estimation and frequency detection for decoding.The element intervals are used to overcome the multi-path effect,improve frequency band effici-ency,and reduce the number of pulses so as to save energy and increase system reliability.Lake trial results show that the rate of data transmission is moderate,coding and decoding are easy to implement,and the system is robust.