Abstract: In October 1983, a comprehensive experiment was carried out to investigate the characteristics of turning-point convergencezones and of underwater sound propagation in a deep sound channel in the South China Sea using explosive sound sources. In this paper, the experimental results for the source at depths of 200 m and 500 m are presented. By using the theory on the turning-point convergence-zone and the parabolic approximation, the measured data are analysed. For low-frequencies measured positions of zones and convergence-gains agree with calculated results very well.