Abstract: While using the bottom bounce mode to detect deep-sea shadow zone, the signal-to-noise ratio decreases due to the influence of the seabed reflection loss on the signal, which poses great difficulties for target detection. Therefore, this article establishes a signal model based on the propagation law of sound in deep-sea shadow zone and analyzes the multipath structural characteristics of signals in shadow channels. Based on the principle of generalized likelihood ratio test, the detector suitable for target detection in shadow zone is designed according to the single beam multipath structural characteristics and spatial beam splitting characteristics. The simulation results and real data processing results both indicate that the proposed detector has significantly improved detection performance compared to traditional matched filter detectors by extracting and utilizing the multipath structural features of the echo of the shadow zone.