Abstract: The characteristics of auto-correlation and cepstrum of ship-radiated noise observed during 2007 South Sea Experiment are analyzed in this paper.It is found that the multipath time-delay peaks of the cepstrum couldn't be observed in the near range,and as well the auto-correlation method has relative higher signal-to-interference ratio to detect time-delay peak than the cepstrum method.The similar experimental results have never been reported,and show that it is difficult to track the time-delay peak continuously using each one of those traditional method above.Base on the ray acoustics theory and the numerical simulation,these results presented in this paper can be explained by the fact that the absolute amplitudes of time-delay peak of the auto-correlation and that of the cepstrum increase and decrease with a decreasing range,respectively.Moreover,a hybrid multipath time-delay estimation technique combining the auto-correlation method with the cepstrum method is proposed to solve the problem of the continuous tracking of time-delay peak.Finally,the processing results of sea trial data demonstrate the effectiveness and robustness of our proposed method.