Abstract: In order to suppress strong self-interference signals in received signals, a self-interference suppression method based on transfer function fitting and multistage delay estimation is proposed. Firstly, the transfer function of transmitting leakage is estimated by frequency domain deconvolution to construct the basic cancellation signal. Then, the multistage delay estimation based on the cross-correlation method and the cross-spectrum method is used to accurately compensate the cancelling signals to obtain a good self-interference suppression effect. The processing results of the actual sea trial data indicate that the suppression ratio of the proposed method can reach 36 dB, and the signal-to-interference ratio of the detectable echo can be reduced from −30 dB to −55 dB when the unmanned undersea vehicles (UUV) integrated system is used to transmit multi-frame linear frequency modulated (LFM) signals in the working sector of the side array for active detection of the target ship. The same suppression effect is found for the subsequent self-interference signals. The above results indicate that the method can suppress the strong self-interference signal, and presents stability, so that the echo signal submerged in the strong self-interference signal can be detected.