Abstract: Harbor detection and recognition is an important SAR(synthetic aperture radar) remote sensing ocean application. By analyzing the structure and microwave scattering characteristics of harbors, a harbor detection and identification algorithm for SAR remote sensing images based on prior constraint is proposed. A closure measure is defined according to the semi closed characteristics of water to extract harbor water, and the jetties are detected with the multi direction scanning method, so the harbor can be initially detected by combing two results. The entrance direction and the representative points of jetties are determined according to the minimum enclosing rectangle of the harbor. Finally, harbor identification is finished with a closure measure for the coastline between representative points of jetties. Experiments show that the proposed algorithm can detect harbor and the entrance directions accurately, and extracts jetties more completely.