In this paper

we propose a new ship detection model based on SAR imagery.The model uses the Pearson distribution system to simulate the backscattering distribution of ocean surface on SAR imagery.In the Pearson distribution system

four distributions including the Pearson distributions of typeⅠ（γ）

Ⅲ

Ⅳ（Inverse γ） and Ⅵ are employed.Using these four distributions

we build a CFAR equation.A distribution selection machine based on β plane is used to select which distribution is adopted to specified SAR imagery.We can get four equations and the threshold of gray level.Then

using the threshold

the model can find ships from SAR images.Some tests show this model working well.