Abstract: In order to extract water accurately, we analyze the characteristics and the imaging mechanism of the country buildings in the synthetic aperture rader (SAR) images, and find that the water detection is interfered by the shadow of the buildings.Therefore, the water is accurately extracted from the high resolution SAR image after getting rid of the building shadows by the texture method and the knowledge-based building representation.This paper indicates that it can more accurately extract information from the high-resolution SAR images with the tradit ional methods, combining with the knowledge based methods.After extract ing water we can analyze the correlative information farther.