The invention discloses a method for extracting a coastline from an SAR coast image, and belongs to the field of image processing. The method comprises the following steps: acquiring the SAR coast image; determining an initial ocean region and an initial land region in the image; calculating a geometric center of the initial ocean region; starting with the geometric center of the initial ocean region to make rays; determining coastal boundary points on the rays; and sequentially connecting all the coastal boundary points to obtain the coastline. The method provided by the invention solves a problem of speckle noises during extraction of the coastline in a traditional method by using a characteristic that the G0 distribution is sensitive to the surface complexity of a measured region, and is easy to implement, high in operation speed and suitable for large-scale images.