Abstract: Airborne radar detects ship target mainly in sea clutter, and the detection performance is greatly bounded by sea clutter distribution property. This paper analyzes properties of L-band airborne radar echoes and especially those of sea clutter, and then presents pre-processing scheme of sea clutter from the view of ship detection. Classical distribution models namely Rayleigh, Weibull, Lognormal and compound K distribution, are verified with real radar data, which shows that the Lognormal distribution is the best. Therefore, the above preprocessing method and conclusion are meaningful in designing radar detector in practice.