Abstract: According to the working characteristic of the airbrone sonar and acoustic signal transmission, a kind of digitized bi-directional data transmission method through a single-lead coaxial cable is proposed in this paper. The test system designed with this method has a data transmission rate of 3 - 6 Mb/s, transmission range of 500 - 1000 m, and code error rate less than 10^-7. The system has substituted the traditional multi-lead cable, and it has such advantages as high speed transmission rate, long transmission distance, large dynamic range, good ability of anti-disturbance, small volume and light weight. It is very suitable for the case that the volume and weight of cable are strictly limited, and long distance bi-directional underwater sound signals transmission is necessary.