Ships in voyage usually radiate a large number of tonal signals，which are significant for the passive detection of ship targets. The actual underwater environment noise usually manifests as time-domain non-stationary noise. The short-term strong component in non-stationary noise is inevitably introduced into the time-domain integration process of Discrete Fourier Transform(DFT)used for tone detection. The signal-to-noise ratio of tone in the integration result is greatly reduced，and the tonal signal detection performance has deteriorated sharply. To solve the above problem，amplitude normalization is conducted on the processing of DFT results，and the phase difference between segmented tonal signals is compensated. Then，a coherent tone detection method in non-stationary noise is proposed. Simulation results show that the proposed method can reduce the influence of time-domain non-stationary noise fluctuations. Compared with traditional DFT-like methods，the proposed method has better tone detection performance in non-stationary noise background，as well as a coherent processing gain of the adjacent data segments.
