Based on the method of dual backward and forward delay kernels, an improved algorithm of echo hiding in which watermark codes embedded the audio signal is proposed in this paper. The energy of each segment into which the original audio is first divided was computed. The energy threshold of audio segments is set by the given rate of embedding watermark codes. Then the audio segments whose energy value above the energy threshold are embedded with the watermark codes and the secret information is detected with a power cepstrum computing method. The simulation results show that the improved algorithm has a significant improvement in imperceptibility and can remarkably decrease the bit error rate of detected watermark codes.