A micro-doppler period estimation method for ship target is proposed. Under the influence of sea conditions, ship targets are in the micro-motion state, which induces micro-doppler modulation on the radar echo. The micro-doppler parameters of the ship target are closely related to ship structure, target dynamics and so on, which is an important basis for ship target recognition. In this paper, based on the radar echo model of ship target, the modulation characteristics are analyzed, and a fast estimation method of micro-Doppler period is proposed. Firstly, the main body translation of ship target is successfully compensated based on the minimum entropy method; then the Doppler range is located according to the entropy difference between the micro-Doppler area and the noise area; finally, the timefrequency correlation coefficient is calculated to provide the micro-Doppler period estimation. The location of micro-doppler range reduces the computation burden of the time-frequency correlation coefficient, which makes it fast compared to the original algorithm. Under the typical scene and radar parameters, the efficiency of the method is improved by 2. 5 times.