Abstract: Due to the influence of the movement of shipborne platform, sea clutter, multi-target aggregation and environmental interference, the radar echo of ship targets on the sea surface are easily obscured and submerged, which results in the greatly weakened target monitoring capability of shipborne surface wave radar. In order to improve the detection and discovery performance of shipborne surface wave radar, a target detection method based on spectrum refinement and second order synchrosqueezing transform is proposed. Firstly, the frequency refinement of shipborne surface wave radar echo signal is carried out to improve the frequency resolution. Then, the time-frequency distribution characteristics of the target are extracted by the time-frequency analysis method of second-order synchrosqueezing transform. Finally, target detection is realized according to the time-frequency distribution characteristics obtained. The experimental results show that compared with the traditional time-frequency analysis methods such as short-time Fourier transform and wavelet transform, the proposed method not only has better time-frequency aggregation, but also can effectively detect moving targets near sea clutter and multi-ship aggregation targets with small echo Doppler frequency difference.