An audio watermarking system based on multiple echoes hiding is designed for frequency modulation (FM) broadcasting. The embedded watermarking information of 16 bits can be recovered from the receiver by recording the broadcast for any 1 second. On the premise of guaranteeing the high imperceptibility and robustness, the multiple echoes scheme we proposed has a higher capacity. The proposed system is tested on a semi-physical platform with the real channel transmission and the recovery rate reaches higher than 98%. Some attacks, such as white noise, filtering, re-sampling, adding an echo and re-quantization, are used to test the robustness. The subjective test result shows that the system has a good imperceptibility.